CN109115940B - Iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramic - Google Patents
Iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramic Download PDFInfo
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Abstract
The invention discloses an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics, belonging to the technical field of ceramic component analysis. The method comprises the following steps: grinding a ceramic sample into powder, and weighing the powder in a round-bottom flask; adding concentrated hydrochloric acid, stirring until the concentrated hydrochloric acid is completely dissolved, and marking the color to be brown yellow; adding the sodium thiosulfate standard solution into a burette, and recording the scale number; adding potassium iodide into the brown yellow solution, covering a bottle stopper, vacuumizing, introducing nitrogen, stirring uniformly until the marked color is reddish brown, titrating to light brown yellow by using a sodium thiosulfate standard solution, adding a starch solution until the marked color is dark blue, and titrating to disappear blue by using the sodium thiosulfate standard solution; recording the scale number after the sodium thiosulfate standard solution is added twice, and calculating the total consumption amount; and (4) calculating the valence state of Fe ions in the ceramic sample, and then obtaining the concentration of oxygen vacancies by utilizing charge balance. The invention has the advantages of simple experimental instrument, simple operation, accurate and reliable detection result and capability of quantitatively analyzing the concentration of the oxygen vacancy.
Description
Technical Field
The invention belongs to the technical field of ceramic component analysis, and particularly relates to an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramic.
Background
The piezoelectric ceramics are functional materials with piezoelectric effect, can realize the interconversion between mechanical energy and electric energy, and are widely applied to the fields of aerospace, military, medical treatment and the like. Bismuth ferrite is a high-temperature ferroelectric, has ferroelectricity and ferromagnetism above room temperature, has Curie temperature of 830 ℃, Nile temperature of 370 ℃, and theoretical spontaneous polarization of about 100 mu C/cm2In recent years, lead-free piezoelectric ceramics have been studied. However, the synthesis temperature range of bismuth ferrite is narrow, bismuth oxide is extremely easy to volatilize in the sintering process to form bismuth vacancies and oxygen vacancies, and the existence of the oxygen vacancies causes Fe3+→Fe2+The conversion causes the insulation resistance to be reduced and the leakage conductance to be increased. The problem of leakage and conduction of bismuth ferrite causes the problem that bismuth ferrite is related to bismuth ferriteThe polarization of the lead-free piezoelectric ceramic series materials is difficult, which greatly limits the application of the lead-free piezoelectric ceramic series materials in practical devices. Therefore, quantitative analysis of the oxygen vacancy concentration has very important scientific significance and application value for researching the influence mechanism of the leakage conductance of the bismuth ferrite-based lead-free piezoelectric ceramic and improving the electrical property of the bismuth ferrite-based lead-free piezoelectric ceramic.
The existing method for analyzing the concentration of oxygen vacancies is to measure the photoelectron spectrum of iron by using X-ray photoelectron spectrum, qualitatively describe the existence or not of metallic iron, ferrous iron and ferric iron ions according to the combination energy and peak type of the photoelectron spectrum, and further describe the quantity of the metallic iron, ferrous iron and ferric iron ions in a semi-quantitative manner by adopting a peak separation mode, thereby qualitatively researching the change trend of the concentration of oxygen vacancies. However, the fluctuation range of the measured result of the method is large, and quantitative description is difficult.
The spectral colorimeter measures the spectral distribution of an object by using a spectral principle, and calculates the tristimulus values and other chromaticity parameters of the color of the object. The essence of this colorimetric method is to measure the spectral reflectance factor R (λ) of a non-transparent object or the spectral transmittance τ (λ) of a transparent object by a comparative method. The color information of the product can be obtained in time, and the production efficiency is effectively improved.
The iodine titration method utilizes the principle of redox reaction to measure the content of high-valence metal ions, and then utilizes a defect equilibrium equation to obtain the non-stoichiometric value of oxygen in the material, and can be used for measuring the oxygen content of high-temperature conductors, solid oxide fuel cells and the like. However, different people have different color resolving power, and bismuth ferrite based lead-free piezoelectric ceramic is an insulating material and contains less oxygen vacancies, and when the color is judged by naked eyes to determine the titration end point, measurement errors are easily caused, so that the experimental result is not accurate, and therefore, the iodine titration method for measuring the concentration of the oxygen vacancies in the bismuth ferrite based lead-free piezoelectric ceramic is rarely reported.
Disclosure of Invention
The invention aims to provide an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics, which has the advantages of simple and convenient experimental instrument, simple operation, accurate and reliable detection result and capability of quantitatively analyzing the oxygen vacancy concentration compared with the traditional iodine titration method.
In order to achieve the purpose, the invention provides the following technical scheme: an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics comprises the following steps:
step 1: grinding a ceramic sample into powder, and weighing 0.1000-4.2224 g of the powder sample in a round-bottom flask;
step 2: adding 5-280 mL of concentrated hydrochloric acid into the powder sample, and stirring until the concentrated hydrochloric acid is completely dissolved, wherein the color of the marking solution is brown yellow;
and step 3: adding the sodium thiosulfate standard solution into a burette, and recording the scale number V1；
And 4, step 4: adding 0.1000-5.5557 g of potassium iodide into the brown yellow solution, covering a bottle stopper, vacuumizing for 1-5 min, introducing nitrogen, stirring uniformly in a nitrogen environment, titrating the red brown solution to light brown yellow by using a sodium thiosulfate standard solution, adding 1-10 mL0.5% of starch solution, wherein the color of the marking solution is dark blue, and continuously titrating the dark blue solution by using the sodium thiosulfate standard solution until the blue color disappears;
and 5: recording the scale number V after adding the sodium thiosulfate standard solution twice2And then the total consumption amount V of the sodium thiosulfate standard solution is V ═ V2-V1；
Step 6: calculating the valence state of Fe ions in the ceramic sample, obtaining the concentration of oxygen vacancies by utilizing charge balance,
wherein, the step 4 further comprises the following steps: the color of the standard sample was used to determine the titration process and each step was performed in sequence.
Further, the method adopts a magnetic stirrer for stirring.
Further, the method uses a spectrophotometer to detect the color change in the reaction process, and the titration process is determined according to the color change.
Further, the preparation method of the standard sample comprises the following steps:
weighing 0.0564-3.1447 g of bismuth oxide and 0.0194-1.0778 g of iron oxide, adding 5-280 mL of concentrated hydrochloric acid, and stirring by using a magnetic stirrer until the bismuth oxide and the iron oxide are completely dissolved to obtain a required solution;
adding 0.1000-5.5557 gKI into the obtained solution, then titrating a sodium thiosulfate standard solution, adding a starch indicator when the color becomes light, marking the color to be dark blue, continuing titrating the sodium thiosulfate solution, recording the color change of each stage when the blue disappears, and measuring the color spectrum of each stage.
Further, a spectrocolorimeter is used to measure the color spectrum of each stage.
Further, the ceramic sample is bismuth ferrite-based lead-free piezoelectric ceramic.
Further, the chemical formula of the ceramic sample is represented as: [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Wherein A represents an element for replacing Bi, M represents an element for replacing Fe, a and b respectively represent the valence states of A, M (a and b can be +2, +3 or +4 valences respectively), 2+ p represents the average valence state of iron ions (p is more than or equal to 0 and less than or equal to 1), (1-x), x, (1-y) and y respectively represent the stoichiometric ratio of Bi, A, Fe and M (x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1), and n represents the oxygen vacancy concentration (n is more than or equal to 0 and less than or equal to 0.5).
Further, the chemical formula of the ceramic sample is (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Is calculated by the following formula [ Bi(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The mass of (A):
in the formula: m isGeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Mass of (c), g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Is prepared from (A) and (B)Molar mass, g/mol;
Mgeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3The molar mass of (a), g/mol,
(1-z) [ Bi ] was calculated according to the following formula(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Molar mass of (a):
Mgeneral assembly＝(1-z)M+zMBT
In the formula: m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
MBTdenotes BaTiO3Molar mass of (a), g/mol.
Further, step 6 specifically includes the following steps:
(1) calculating the valence state of iron
In the formula: c represents the concentration of a standard solution of sodium thiosulfate and has the unit of mol/L;
v represents the volume of the standard solution of sodium thiosulfate consumed by the sample and is expressed by L;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The mass of (d) in g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The molar mass of (a) in g/mol,
(2) calculating the oxygen vacancy concentration in the sample:
in the formula: 2+ p represents the average valence of the iron ion;
a is the valence state of A;
x is the doping amount of A;
b is the valence state of M;
y is the doping amount of M.
The beneficial effects of the invention are as follows:
1. the titration process of the iodometry is further accurate, the ferric oxide and the bismuth oxide are directly used for preparing the standard sample solution and are used as the judgment basis of the titration process, so that the measurement error caused by the fact that the color is difficult to distinguish by naked eyes is avoided, the titration end point can be better judged, and the measurement result is accurate and reliable.
2. Compared with the method for analyzing the oxygen vacancy concentration by using X-ray photoelectron spectroscopy, the iodometry method for determining the oxygen vacancy concentration in the bismuth ferrite-based lead-free piezoelectric ceramic has the advantages of short time, greatly shortened detection period, low cost and suitability for batch and rapid detection.
3. The invention titrates the bismuth ferrite-based lead-free piezoelectric ceramic sample solution to be light yellow in the process of titrating the bismuth ferrite-based lead-free piezoelectric ceramic sample solution, namely, the starch solution is added when the titration end point is approached, thereby preventing the adsorption I from being added prematurely2And adding the titration too late to exceed the end point, so that the measurement result is influenced, and the obtained titration result is close to the true value.
4. The experimental instrument used in the invention is simple, the operation steps are simple, and the operation is convenient. Before the reaction, the vacuum pumping is carried out, the reaction process is carried out in a nitrogen environment, the influence of factors such as oxygen and the like is eliminated, and the accuracy of the detection result is improved.
Drawings
FIG. 1 is a diagram of an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics;
FIG. 2 is a flow chart of a method for determining the iodine content of oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics according to the invention;
FIGS. 3a to 3e are diagrams of color change and UV-VIS absorption spectra of the solutions of the standard samples;
FIGS. 4a to 4e are color change diagrams in the experimental process of determining the oxygen vacancy concentration in the bismuth ferrite-based lead-free piezoelectric ceramic;
reference numerals:
FIG. 1:
1-basic burette 2-iron support 3-glass catheter 4-rubber stopper
5-air bag 6-round flask 7-magnetic rotor
8-magnetic stirrer 9-three-way glass tube
FIG. 3 a-the color of the iron oxide and bismuth oxide after dissolution, i.e., tan;
FIG. 3 b-color after addition of KI, i.e.reddish brown;
FIG. 3 c-color before addition of starch, i.e. light brown-yellow;
FIG. 3 d-color after addition of starch, i.e. dark blue;
FIG. 3 e-the final reacted color, i.e.light yellow.
FIG. 4 a: 1) the color of the sample after dissolution, i.e. brown-yellow;
FIG. 4 b: 2) adding KI to obtain reddish brown color;
FIG. 4 c: 3) the color before adding starch, i.e. light brown-yellow;
FIG. 4 d: 4) the color after adding starch, namely dark blue;
FIG. 4 e: 5) the final reacted color was light yellow.
Detailed Description
The present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The following will further explain the preparation method and practical effects of the present invention by combining the specific embodiments and the accompanying drawings. The examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention.
The invention will now be further described with reference to specific embodiments
Principle of experiment of the invention
The bismuth ferrite based lead-free piezoelectric ceramic sample is dissolved by concentrated hydrochloric acid, and the average valence state of iron ions in the sample is between +2 and + 3;
assuming that the average valence of iron ion is 2+ p, Fe is in acidic environment2+pReaction with excess KI to form I2And Fe2 +This is a reversible reaction which proceeds quantitatively to the right in the presence of excess KI, which is Fe2+pIs also a reducing agent of2A complex of (a); in order to prevent oxygen in the air from influencing, KI is added, vacuum pumping is immediately carried out, nitrogen is introduced, then sodium thiosulfate standard titration solution is used for titration, and starch solution is added when titration is carried out to be faint yellow, namely the titration end point is approached (when the color is darker, I is adsorbed by adding the starch solution2Molecules, added when the color is lighter, titrate easily beyond the endpoint).
The color of each substance has unique spectral distribution, the tristimulus values and other chromaticity parameters of the object color are calculated and compared with the color of the standard substance, the product color information can be obtained in time, and the reaction process is judged.
The relevant reactions are as follows:
the equipment used in the invention: an electronic balance: the mixture can be precisely weighed to 0.0001g, a pipette, a 100-500 mL three-neck flask, a magnetic stirrer, a vacuum pump, a 10-100 mL alkali burette, a balloon, vacuum silicone grease, a nitrogen cylinder, a rubber tube, a clamp, a frame, a spectrophotometer and a UV-6100 DOUBLEBEAMSPECTROPHOTOMETER;
the reagents used in the invention: concentrated hydrochloric acid, potassium iodide (solid), 0.1mol/L sodium thiosulfate standard solution, 0.5% starch solution and (1-z) BiFeO3-zBaTiO3(z＝0.20，0.25，0.30，0.35，0.40)、0.7Bi(Fe1-yMy)O3-0.3BaTiO3(M＝Sc；y＝0.00，0.02，0.04，0.06，0.08)、(Bi1-xAx)FeO3(A ═ Sr, Ca ═ x ═ 0.40, 0.45, 0.50, 0.55) sample, OxidationBismuth, iron oxide.
FIG. 1 is a diagram of an iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics, which comprises the following steps: the device comprises an alkali burette 1, an iron support 2, a glass conduit 3, a rubber stopper 4, an air bag 5, a round-bottom flask 6, a magnetic rotor 7, a magnetic stirrer 8 and a three-way glass tube 9.
The judgment of the titration process of the iodometry is related to the success and failure of the whole experiment, but the color resolution capabilities of different people are different, and when the titration process is judged by naked eyes and a sodium thiosulfate standard titration solution is dripped, measurement errors are easily caused, so that the accuracy of the experiment is influenced, the errors can be eliminated in the titration process of the judgment analysis sample according to the color change spectrum of the standard sample, and therefore, the standard sample needs to be prepared for the judgment of the reaction process.
After bismuth ferrite is dissolved in hydrochloric acid, iron ions and bismuth ions are present, so that a standard sample can be prepared from bismuth oxide and iron oxide of the same molar mass. When the excessive sodium thiosulfate standard solution is added into the air, iodide ions in the solution cannot be oxidized, and the color cannot be influenced by oxygen in the air, so that the color change process can be used as a judgment basis in the reaction process.
1. Preparation of Standard samples
Weighing 0.0564g to 3.1447g of bismuth oxide and 0.0194g to 1.0778g of iron oxide, adding 5mL to 280mL of concentrated hydrochloric acid, and stirring by a magnetic stirrer until the bismuth oxide and the iron oxide are completely dissolved to obtain the required solution.
2. Determination of the colour spectrum of a standard sample
And (3) adding 0.1000-5.5557 gKI into the solution in the step (1), then titrating the sodium thiosulfate standard solution, adding a starch indicator when the color becomes light, continuing to titrate the sodium thiosulfate solution when the color becomes dark blue, and ending the titration when the blue color disappears. The color change of each stage is recorded, and the color spectrum of each stage is measured by a spectrocolorimeter.
As shown in FIG. 2, the method for determining the iodine content of the oxygen vacancy concentration in the bismuth ferrite-based lead-free piezoelectric ceramic according to the invention specifically comprises the following steps:
(1) weigh 0.0564g &3.1447g bismuth oxide (Bi)2O3) Powder and 0.0194 to 1.0778g of iron oxide (Fe)2O3) Putting the powder into a round-bottom flask, adding 5-280 mL of concentrated hydrochloric acid, stirring by using a magnetic stirrer until the concentrated hydrochloric acid is completely dissolved, adding excess KI (0.1000-5.5557 g), and then titrating sodium thiosulfate (Na)2S2O3) And (3) adding a starch indicator when the color of the standard solution becomes light, wherein the color is dark blue, continuously dropwise adding the sodium thiosulfate standard solution, and stopping titration when the blue color disappears. The color of each stage was noted and a small amount of the solution was taken to measure the uv-vis absorption spectrum, and then the color of each stage was used as a standard for titration, as shown in fig. 3a to 3 e.
(2) Grinding a ceramic sample into powder in an alumina mortar, weighing 0.1000-4.2224 g of the powder sample in a 100-500 mL round-bottom flask, adding 5-280 mL of concentrated hydrochloric acid, and stirring by using a magnetic stirrer until the concentrated hydrochloric acid is completely dissolved to obtain a brown yellow solution, wherein the brown yellow solution is shown in an attached figure 4 a;
(3) adding excessive KI (0.1000-5.5557 g) into the solution in the step (1), quickly covering the bottle mouth, vacuumizing for 1-5 min, and introducing nitrogen. Stirring with a magnetic stirrer under nitrogen atmosphere to obtain reddish brown solution as shown in FIG. 4 b. The sodium thiosulfate standard solution was titrated and the reddish brown slowly faded to a pale brownish yellow color as shown in figure 4 c. At this point, 1-10 ml of 0.5% starch indicator was added, and the solution turned dark blue as shown in FIG. 4 d. Titration of the sodium thiosulfate standard solution was continued and stopped when the blue color disappeared, as shown in FIG. 4 e. In this process, the color of the standard sample is used to determine the titration process and each step is performed in sequence.
(4) And calculating the average valence state of Fe ions in the ceramic sample according to the total consumption amount of the sodium thiosulfate standard solution, and then obtaining the concentration of oxygen vacancies by utilizing charge balance.
The analysis method as described above, preferably, the method further comprises calculation of the analysis result, and the chemical formula of the sample is represented as: [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Wherein A represents an element substituted for Bi, and M represents an element substituted for FeA and b respectively represent the valence states of A, M (a and b can be +2, +3 or +4 valences respectively), 2+ p represents the average valence state of iron ions (p is more than or equal to 0 and less than or equal to 1), (1-x), x, (1-y), y respectively represents the stoichiometric ratio of Bi, A, Fe and M (x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1), and n represents the oxygen vacancy concentration (n is more than or equal to 0 and less than or equal to 0.5).
Further, step 6 specifically includes the following steps:
(1) calculating the valence state of iron
In the formula: c represents the concentration of a standard solution of sodium thiosulfate and has the unit of mol/L;
v represents the volume of the standard solution of sodium thiosulfate consumed by the sample and is expressed by L;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The mass of (d) in g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The molar mass of (a) in g/mol,
(2) calculating the oxygen vacancy concentration in the sample:
in the formula: 2+ p represents the average valence of the iron ion.
a is the valence state of A;
x is the doping amount of A;
b is the valence state of M;
y is the doping amount of M.
If it is (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Then, the mass needs to be calculated by the following formula:
in the formula: m isGeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Mass of (c), g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
Mgeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Molar mass of (a), g/mol;
(1-z) [ Bi ] was calculated according to the following formula(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Molar mass of (a):
Mgeneral assembly＝(1-z)M+zMBT
In the formula: m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
MBTdenotes BaTiO3Molar mass of (a), g/mol;
example 1
In this example, a set of (1-z) BiFeO3-zBaTiO3(z ═ 0.20, 0.25, 0.30, 0.35, 0.4) the sample was taken as an example, and the specific measurement method steps were as follows:
1. sample weighing
Taking 0.7BiFeO3-0.3BaTiO3(z ═ 0.30) of the ceramic sample, pulverized with an alumina mortar, and 0.1000g of the powder sample was accurately weighed with an electronic balance.
2. Sample dissolution
Placing the weighed powder sample into a 100mL three-neck round-bottom flask, adding 5mL concentrated hydrochloric acid, and stirring by using a magnetic stirrer until the mixture is stirredTransferring the standard sodium thiosulfate solution into a burette by a pipette, and reading down the scale number V1。
3. Titration of samples
Adding 0.1000g of potassium iodide into the solution, immediately covering a bottle stopper, vacuumizing for 1min, introducing nitrogen, uniformly stirring by using a magnetic stirrer, titrating the solution to light brown-yellow by using a sodium thiosulfate standard solution, adding 1ml of 0.5% starch solution to mark the solution to be dark blue, continuously titrating by using the sodium thiosulfate standard solution until the blue color disappears, and in the process, judging the titration process by using the color of a standard sample and sequentially carrying out each step of operation. The total amount V of sodium thiosulfate standard solution added twice is recorded2And the consumption V of the standard sodium thiosulfate solution is equal to V2-V1。
4. Calculation of analysis results
The chemical formula of the sample is represented as: (1-z) BiFe(2+p)O(3-n)-zBaTiO3
The oxygen vacancy concentration in the sample was calculated according to the following formula:
in the formula: 2+ p represents the average valence of the iron ion;
the average valence state of the iron ion is calculated according to the following formula:
in the formula: c represents the concentration of a standard solution of sodium thiosulfate, and mol/L;
v represents the total consumption of the sodium thiosulfate standard solution, L;
m represents BiFe(2+p)O(3-n)Molar mass of (a), g/mol;
m represents BiFe(2+p)O(3-n)Mass of (c), g;
BiFe was calculated according to the following formula(2+p)O(3-n)The mass of (A):
in the formula: m isGeneral assemblyRepresents (1-z) BiFe(2+p)O(3-n)-zBaTiO3Mass of (c), g;
m represents BiFe(2+p)O(3-n)Molar mass of (a), g/mol;
Mgeneral assemblyRepresents (1-z) BiFe(2+p)O(3-n)-zBaTiO3Molar mass of (a), g/mol;
(1-z) BiFe was calculated according to the following formula(2+p)O(3-n)-zBaTiO3Molar mass of (a):
Mgeneral assembly＝(1-z)M+zMBT
In the formula: m represents BiFe(2+p)O(3-n)Molar mass of (a), g/mol;
MBTdenotes BaTiO3The molar mass of (a), g/mol;
the procedure for measuring the oxygen vacancy concentration of the sample at z-0.20, 0.25, 0.35, 0.4 was exactly the same as in example 1, and the experimental results are shown in table 1 below.
TABLE 1
Example 2
In this example, a set of 0.7Bi (Fe)1-yMy)O3-0.3BaTiO3(M ═ Sc; y ═ 0.00, 0.02, 0.04, 0.06, 0.08) the samples were taken as examples and the specific procedure of the measurement was as follows:
1. sample weighing
Taking 0.7BiFeO3-0.3BaTiO3(y ═ 0.00) of the ceramic sample, pulverized with an alumina mortar, and 0.6032g of the powder was accurately weighed with an electronic balanceAnd (3) sampling.
2. Sample dissolution
Placing the weighed powder sample into a 100mL three-neck flask, adding 30mL concentrated hydrochloric acid, stirring with a magnetic stirrer until the bottom of the solution is totally white precipitate which is barium titanate and insoluble in concentrated hydrochloric acid, transferring the sodium thiosulfate standard solution into a burette by a pipette, and reading the scale number V1。
3. Titration of samples
Adding 0.6000g of potassium iodide into the solution, immediately covering a bottle stopper, vacuumizing for 1min, introducing nitrogen, uniformly stirring by using a magnetic stirrer, titrating the solution to light brown-yellow by using a sodium thiosulfate standard solution, adding 3mL of starch solution to mark the solution to be dark blue, continuously titrating by using the sodium thiosulfate standard solution until the blue color disappears, and in the process, judging the titration process by using the color of a standard sample and sequentially carrying out each step of operation. The total amount V of sodium thiosulfate standard solution added twice is recorded2And the consumption V of the standard sodium thiosulfate solution is equal to V2-V1。
4. Calculation of analysis results
The chemical formula of the sample is represented as: 0.7Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)-0.3BaTiO3
The oxygen vacancy concentration in the sample was calculated according to the following formula:
in the formula: b represents the valence of M;
y represents the doping amount of M;
2+ p represents the average valence of the iron ion;
the average valence state of the iron ion is calculated according to the following formula:
in the formula: c represents the concentration of a standard solution of sodium thiosulfate, and mol/L;
v represents the total consumption of the sodium thiosulfate standard solution, L;
m represents Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
m represents Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)Mass of (c), g;
bi [ Fe ] was calculated according to the following formula(2+p) (1-y)Mb y]O(3-n)The mass of (A):
in the formula: m isGeneral assemblyRepresents 0.7Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)-0.3BaTiO3Mass of (c), g;
m represents Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
Mgeneral assemblyRepresents 0.7Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)-0.3BaTiO3Molar mass of (a), g/mol;
the 0.7Bi [ Fe ] is calculated according to the following formula(2+p) (1-y)Mb y]O(3-n)-0.3BaTiO3Molar mass of (a):
Mgeneral assembly＝0.7M+0.3MBT
In the formula: m represents Bi [ Fe ](2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
MBTdenotes BaTiO3The molar mass of (a), g/mol;
the procedure for measuring the oxygen vacancy concentration of the sample was exactly the same as in example 1 except that y was 0.02, 0.04, 0.06 or 0.08, and the experimental results are shown in table 2 below.
TABLE 2
Example 3
In this embodiment, a set of [ Bi ] s1-xAx]FeO3For example, (a ═ Sr, Ca; x ═ 0.00, 0.40, 0.45, 0.50, 0.55) the sample was measured by the following specific measurement procedures:
1. sample weighing
Taking BiFeO3(x ═ 0.00) of the ceramic sample, pulverized with an alumina mortar, and 4.2224g of the powder sample was accurately weighed with an electronic balance.
2. Sample dissolution
Placing the weighed powder sample into a 500mL three-neck flask, adding 280mL concentrated hydrochloric acid, stirring by a magnetic stirrer until the solution is completely dissolved, transferring the sodium thiosulfate standard solution into a burette by a pipette, and reading the scale number V1。
3. Titration of samples
Adding 5.5557g of potassium iodide into the solution, immediately covering a bottle stopper, vacuumizing for 5min, introducing nitrogen, uniformly stirring by using a magnetic stirrer, titrating the solution to light brown yellow by using a sodium thiosulfate standard solution, adding 10mL of starch solution until the color of the labeled solution is dark blue, continuously titrating by using the sodium thiosulfate standard solution until the blue color disappears, and in the process, judging the titration process by using the color of a standard sample and sequentially carrying out each step of operation. The total amount V of sodium thiosulfate standard solution added twice is recorded2And the consumption V of the standard sodium thiosulfate solution is equal to V2-V1。
4. Calculation of analysis results
The chemical formula of the sample is represented as: [ Bi ](1-x)Aa x]Fe(2+p)O(3-n)
The oxygen vacancy concentration in the sample was calculated according to the following formula:
in the formula: 2+ p represents the average valence of the iron ion;
x represents the doping amount of A;
a represents the valence of A.
The average valence state of the iron ion is calculated according to the following formula:
in the formula: c represents the concentration of a standard solution of sodium thiosulfate, and mol/L;
v represents the total consumption of the sodium thiosulfate standard solution, L;
m represents [ Bi ](1-x)Aa x]Fe(2+p)O(3-n)Molar mass of (a), g/mol;
m represents [ Bi ](1-x)Aa x]Fe(2+p)O(3-n)Mass of (c), g;
Bi(1-x)AxFeO3the procedure for measuring the oxygen vacancy concentration of the sample (a ═ Sr, Ca; x ═ 0.40, 0.45, 0.50, 0.55) was exactly the same as in example 3, and the experimental results are shown in tables 3 to 4 below.
TABLE 3 Bi1-xSrxFeO3Examples
TABLE 4 Bi1-xCaxFeO3Examples
While embodiments of the present invention have been presented herein, it will be appreciated by those skilled in the art that changes may be made to the embodiments herein without departing from the spirit of the invention. The above examples are merely illustrative and should not be taken as limiting the scope of the invention.
Claims (8)
1. An iodine amount method for determining oxygen vacancy concentration in bismuth ferrite-based lead-free piezoelectric ceramics is characterized by comprising the following steps:
step 1: grinding a ceramic sample into powder, and weighing 0.1000-4.2224 g of the powder sample in a round-bottom flask;
step 2: adding 5-280 mL of concentrated hydrochloric acid into the powder sample, and stirring until the concentrated hydrochloric acid is completely dissolved, wherein the color of the marking solution is brown yellow;
and step 3: adding the sodium thiosulfate standard solution into a burette, and recording the scale number V1；
And 4, step 4: adding 0.1000-5.5557 g of potassium iodide into the brown yellow solution, covering a bottle stopper, vacuumizing for 1-5 min, introducing nitrogen, stirring uniformly in a nitrogen environment, titrating the red brown solution to light brown yellow by using a sodium thiosulfate standard solution, adding 1-10 mL0.5% of starch solution, wherein the color of the marking solution is dark blue, and continuously titrating the dark blue solution by using the sodium thiosulfate standard solution until the blue color disappears;
and 5: counting the scale number after adding the sodium thiosulfate standard solution twice, and determining the total consumption amount V of the sodium thiosulfate standard solution as V2-V1；
Step 6: calculating the valence state of Fe ions in the ceramic sample, obtaining the concentration of oxygen vacancies by utilizing charge balance,
wherein, the step 4 further comprises the following steps: the color of the standard sample is used to determine the titration process and each operation is performed in turn,
wherein, the preparation method of the standard sample comprises the following steps:
weighing 0.0564-3.1447 g of bismuth oxide and 0.0194-1.0778 g of iron oxide, adding 5-280 mL of concentrated hydrochloric acid, and stirring by using a magnetic stirrer until the bismuth oxide and the iron oxide are completely dissolved to obtain a required solution;
adding 0.1000-5.5557 gKI into the obtained solution, then titrating a sodium thiosulfate standard solution, adding a starch indicator when the color becomes light, marking the color to be dark blue, continuing titrating the sodium thiosulfate solution, recording the color change of each stage when the blue disappears, and measuring the color spectrum of each stage.
2. The method of claim 1, wherein the method uses a magnetic stirrer for stirring.
3. The method of claim 1, wherein the method comprises detecting a color change during the reaction with a spectrophotometer, and determining the progress of the titration.
4. The method of claim 1, wherein the color spectra of each stage are measured using a spectrocolorimeter.
5. The method of claim 1, wherein the ceramic sample is a bismuth ferrite-based lead-free piezoelectric ceramic.
6. The method of claim 5, wherein the ceramic sample has a chemical formula of: [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Wherein A represents an element for replacing Bi, M represents an element for replacing Fe, a and b respectively represent the valence states of A, M, and a and b are +2 valence, +3 valence or +4 valence; 2+ p represents the average valence state of iron ions, and p is more than or equal to 0 and less than or equal to 1; (1-x), x, (1-y) and y respectively represent the stoichiometric ratio of Bi, A, Fe and M, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1; n represents the oxygen vacancy concentration, and n is more than or equal to 0 and less than or equal to 0.5.
7. The method of claim 5, wherein the ceramic sample has a chemical formula of (1-z) [ Bi ™(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Is calculated by the following formula [ Bi(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The mass of (A):
in the formula: m isGeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Mass of (c), g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
Mgeneral assemblyRepresents (1-z) [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3The molar mass of (a), g/mol,
(1-z) [ Bi ] was calculated according to the following formula(1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)-zBaTiO3Molar mass of (a):
Mgeneral assembly＝(1-z)M+zMBT
In the formula: m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)Molar mass of (a), g/mol;
MBTdenotes BaTiO3Molar mass of (a), g/mol.
8. The method according to claim 6 or 7, characterized in that step 6 comprises in particular the steps of:
(1) calculating the valence state of iron
In the formula: c represents the concentration of a standard solution of sodium thiosulfate and has the unit of mol/L;
v represents the volume of the standard solution of sodium thiosulfate consumed by the sample and is expressed by L;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The mass of (d) in g;
m represents [ Bi ](1-x)Aa x][Fe(2+p) (1-y)Mb y]O(3-n)The molar mass of (a) in g/mol,
(2) calculating the oxygen vacancy concentration in the sample:
in the formula: 2+ p represents the average valence of the iron ion;
a is the valence state of A;
x is the doping amount of A;
b is the valence state of M;
y is the doping amount of M.
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