CN114751734A

CN114751734A - Dielectric material for low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor and preparation method thereof

Info

Publication number: CN114751734A
Application number: CN202210472445.4A
Authority: CN
Inventors: 邢孟江; 曲明山; 杨鸿宇; 乔峰; 阮丽梅
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-07-15
Anticipated expiration: 2042-04-29
Also published as: CN114751734B

Abstract

The invention belongs to the field of electronic ceramics and manufacture thereof, in particular to a dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor and a preparation method thereof; by adding in Mg_0.17Nb_0.33Ti_0.5O₂Composite ion V is introduced into main material⁵⁺And Ta⁵⁺Partial substitution of ions is carried out, and simultaneously a modifier A is designed and doped₂CO₃‑BO‑C₂O₃‑SiO₂(A ═ Na, Li; B ═ CaO, MgO, CuO; C ═ B, Nd), provides a negative temperature coefficient of permittivity of-330. + -. 30 ppm/DEG C while significantly lowering the sintering temperature, and reduces the deterioration factor of loss due to modifiers, and is preparedThe dielectric material has low loss, low cost and good process stability and is applied to radio frequency MLCC.

Description

Dielectric material for low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor and preparation method thereof

Technical Field

The invention belongs to the field of electronic ceramics and manufacturing thereof, and relates to a dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor and a preparation method thereof.

Background

In recent years, with the rapid development of the fifth generation mobile communication technology (5G), demands for electronic components have also been shifted to high performance, high frequency, and miniaturization. The chip multilayer Ceramic capacitor (MLCC) has many advantages such as being suitable for high frequency or ultra high frequency, small in volume, large in specific volume, long in service life, high in safety and the like, plays a great role in the field of communication, and the demand of the MLCC is increased year by year.

The MLCC consists of three parts, namely an internal electrode, a terminal electrode and a ceramic medium layer, wherein the internal electrode (such as an Ag electrode) and the ceramic medium layer are mutually parallel to form a main body, and the terminal electrode is generally of a three-layer structure: the innermost layer plays a role of linking and leads out an inner electrode; the middle part is a barrier layer which mainly prevents Ag from being corroded by molten soldering tin during welding; the outermost layer is a welding layer. Classification of ceramic capacitors is often based on the temperature coefficient of permittivity τ of the dielectric ceramic employed_εAnd (4) showing. Ceramic media are generally classified into three broad categories, class I, class II and class III ceramics, based on temperature stability, according to the American society for electronics and industry RS-198 standards. Among them, the class i ceramic capacitor has high stability and low loss characteristics, and is most widely used in radio frequency and microwave communication applications. The naming rule of the dielectric ceramic capacitor is different according to the temperature characteristic of the dielectric constant, for example, the ceramic capacitor with the temperature characteristic of S2G has the temperature drift of-330 +/-30 ppm/DEG C in the temperature range (-55-85 ℃), and the dielectric ceramic capacitor can be used for preparing circuits of T/R components of phase-controlled radars, radio frequency power amplifiers, transmitters and the like to play the roles of coupling, coordination, filtering and the like.

Common class I ceramic capacitors are made with TiO₂Based on, e.g. ZnO-MgO-TiO ₂Is BaO-TiO₂And BaO-La₂O₃-TiO₂And the sintering temperature of the system is too high (more than or equal to 1350 ℃), so that the energy consumption and the cost are increased. Systems surround TiO₂Spreading out, e.g. by ion doping or multi-phase recombinationThe processes improve the dielectric property and reduce the sintering temperature, thereby increasing the practicability.

Utilizing (Mg)_1/3Nb_2/3)⁴⁺Composite ion substituted TiO₂When the amount of substitution is low, rutile structure Mg is formed_0.17Nb_0.33Ti_0.5O₂Indicates that the complex ion does not cause TiO₂The structural change is reported in the literature, and the sintering temperature of the ceramic is reduced to a certain extent, and the dielectric property is correspondingly deteriorated: epsilon _r80, Qxf-8500 GHz; although researchers have also studied Mg_0.17Ta_0.33Ti_0.5O₂Ceramics, which are excellent in dielectric properties: epsilon_r65, Qxf 18000GHz, but the sintering temperature is still high (1250 ℃), which is not suitable for practical application.

In combination with the above current research situation, it is not difficult to find Mg in the prior art_0.17Nb_0.33Ti_0.5O₂The base ceramic has the problems of poor comprehensive dielectric property and the like, such as the fact that excellent dielectric property can not be maintained at a lower sintering temperature. There is a need for improvement to develop a method for co-firing Ag inner electrodes with simple and controllable process, low dielectric loss<950 ℃), and the temperature compensation type MLCC material with stable dielectric constant and temperature coefficient can meet the application requirements of the radio frequency communication industry.

Disclosure of Invention

The invention aims to provide a dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor and a preparation method thereof, so as to overcome the defect of Mg_0.17Nb_0.33Ti_0.5O₂The technical defects of low sintering temperature and excellent dielectric property cannot be simultaneously considered.

In order to realize the purpose, the invention adopts the following technical scheme:

a dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor comprises a ceramic material and a modifier;

the chemical formula of the ceramic material is Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂；

The formula of the modifier is A₂CO₃-BO-C₂O₃-SiO₂(42:12:36:10 wt.%), wherein A is₂CO₃From 16 wt.% Na₂CO₃With 26 wt.% Li₂CO₃Composition is carried out; BO consists of 4 wt.% MgO with 8 wt.% CuO; c₂O₃From 32 wt.% of B₂O₃With 4 wt.% of Nd₂O₃Composition is carried out;

the formulation of the dielectric material for the multilayer ceramic capacitor is Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂+ x wt.% of modifier, wherein x is in the value range of 1 to 2; prepared by a solid phase method, and the main crystal phase of the crystal is rutile type Mg_0.17Nb_0.33Ti_0.5O₂The structure, the sintering temperature is 850-900 ℃; a dielectric constant of 58 to 71 and a dielectric loss of 2X 10^-4～5×10^-4The Q x f value is 8000-18000 GHz, the temperature coefficient of dielectric constant is stable and meets the S2G temperature characteristic (-55 ℃, -334 ppm/DEG C; 85 ℃, -338 ppm/DEG C).

Preferably, when x is 1, the dielectric constant of the material at the sintering temperature of 900 ℃ is 70.6, and the dielectric loss is as low as 2.2 × 10 ^-4The Q x f value of the quality factor is up to 17822 GHz.

The preparation method of the dielectric material for the low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor comprises the following steps:

step 1, adding MgO and TiO₂、Nb₂O₅、V₂O₅And Ta₂O₅According to the chemical formula Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂Burdening is carried out;

and 2, step: putting the powder prepared in the step 1 into a ball milling tank, performing planetary ball milling for 4-6 hours according to the mass ratio of the powder to zirconium balls to deionized water of 1: 5-7: 3-5, drying the mixed slurry in an oven after the ball milling is finished, and then sieving by using a 40-100-mesh sieve; presintering the sieved powder in an atmosphere at 900-1100 ℃ for 3-5 hours;

step 3, adding Na₂CO₃、Li₂CO₃、MgO、CuO、B₂O₃、Nd₂O₃And SiO₂The raw powder materials are mixed according to the mass ratio of 16:26:4:8:32:4:10, then planetary ball milling is carried out for 6-8 hours according to the mass ratio of the powder materials to zirconium balls to alcohol being 1: 5-7: 4-6, after the ball-milled materials are dried, the materials are presintered for 3-6 hours at the temperature of 600-650 ℃, then the materials are heated to 1400-1500 ℃ to be melted for 3-5 hours, the melted glass is rapidly poured into deionized water to be cooled, and the cooled glass materials are ground into uniform fine powder to obtain the modifier;

step 4, modifying the modifier obtained in the step 3 according to Mg _0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂+ x wt.% of modifier (x ═ 1-2) added to the Mg of step 2_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂In the pre-sintering material, and according to the powder: zirconium ball: carrying out planetary ball milling for 3-5 hours at the mass ratio of deionized water of 1: 5-7: 3-5, and after drying ball-milled materials, adding a polyvinyl alcohol solution into powder to carry out bonding granulation;

and 5, pressing and molding the ceramic raw material prepared in the step 4, then carrying out degumming at the temperature of 600-650 ℃ for 3-5 hours at the heating rate of 2-5 ℃/min, then heating to 850-900 ℃ at the same rate, and carrying out heat preservation for 4-6 hours to obtain the low-temperature sintered Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂A dielectric ceramic material.

As is well known, the low-temperature sintering of ceramics is completed by means of a liquid-phase sintering mechanism, that is, the glass frit has a wetting effect on the ceramic matrix, so that the ceramics generates a dissolution phenomenon in a glass liquid phase and completes a dissolution-precipitation process, thereby realizing low-temperature densification. However, the matching of glass to ceramic (including the advantages and disadvantages of wettability and solubility) is unique and unique, and for a specific ceramic matrix, a glass auxiliary agent matched with the specific ceramic matrix needs to be found. By usingThe invention discloses a glass modifier matched with Mg-Ti-Nb ceramic, which is a dielectric material for sintering Mg-Ti-Nb multilayer ceramic capacitors at low temperature, and adopts a mode of combining an ion substitution process and a doping modifier _0.17Nb_0.33Ti_0.5O₂The main material is introduced with compound ion V⁵⁺And Ta⁵⁺Partial substitution of ions is carried out, and simultaneously a modifier A is designed to be doped₂CO₃-BO-C₂O₃-SiO₂The dielectric material (A ═ Na, Li; B ═ CaO, MgO, CuO; C ═ B, Nd) can provide a negative temperature coefficient of dielectric constant of-330 +/-30 ppm/DEG C while the sintering temperature is remarkably reduced, and loss deterioration factors caused by a modifier are reduced, so that the dielectric material applied to radio frequency MLCC with low loss, low cost and good process stability is prepared.

Drawings

Figure 1 XRD spectrum corresponding to example 3;

FIG. 2 corresponds to the SEM topography of example 3.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples.

Step 1: mixing MgO and TiO₂、Nb₂O₅、V₂O₅And Ta₂O₅According to the chemical formula Mg_0.17Nb_0.33Ti_0.5O₂Burdening;

step 2: filling the powder prepared in the step 1 into a ball milling tank, and mixing the following materials: zirconium ball: and (3) carrying out planetary ball milling for 6 hours at the mass ratio of the deionized water to 5 of 1:6:5, drying the mixed slurry in an oven after the ball milling is finished, and then sieving by using a 100-mesh sieve. Presintering the sieved powder in an atmosphere at 950 ℃ for 5 hours;

and step 3: mixing Na₂CO₃、Li₂CO₃、MgO、CuO、B₂O₃、Nd₂O₃And SiO₂The raw powder is prepared according to the mass ratio of 16:26:4:8:32:4:10, and then the raw powder is prepared according to the following steps: zirconium ball: the mass ratio of the alcohol is 1:6 5, performing planetary ball milling for 6 hours, after drying ball-milled materials, presintering the ball-milled materials at 650 ℃ for 4 hours, then heating to 1500 ℃ for melting for 5 hours, quickly pouring the molten glass into deionized water for cooling, and grinding the cooled glass frit into uniform fine powder to obtain the modifier;

and 4, step 4: modifying the modifier obtained in the step 3 according to Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂+ x wt.% of modifier (x ═ 1-2) added to the Mg of step 2_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂In the pre-sintering material, and according to the powder: zirconium ball: carrying out planetary ball milling for 4 hours at the mass ratio of deionized water of 1:6:4, and adding a polyvinyl alcohol solution with the mass percent of 8% into powder of the ball-milled materials after drying the ball-milled materials to serve as a binder for granulation;

and 5: pressing and molding the ceramic raw material prepared in the step 4, then discharging glue at 650 ℃ for 4 hours at the heating rate of 3 ℃/min, then heating to 850-900 ℃ at the same rate, and preserving heat for 6 hours to prepare the low-temperature sintered Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂A dielectric ceramic material.

To better illustrate the effects of the present invention, 6 samples of examples were prepared according to the above procedure. FIG. 1 is the XRD diffraction pattern of example 3, which is searched for the phase composition and Mg of the ceramic_0.17Nb_0.33Ti_0.5O₂The standard card JCPDS card No.40-0366 corresponds to the type of ceramic which is Mg if no second phase diffraction peak is found in the system _0.17Nb_0.33Ti_0.5O₂And (5) structure.

FIG. 2 is the SEM topography of example 3 at which the grain size is small and micro pores are present.

The compositions and microwave dielectric properties of the examples are as follows:

table 1 shows the composition of the sample groups of the examples

Table 2 shows dielectric properties of the samples of each example

From the data shown in tables 1 and 2, it can be seen that in example 3, when the sintering temperature is 900 ℃, Mg after modification_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂The dielectric constant and Q x f value of the ceramic material are optimized as follows: epsilon_r＝70.6，tanδ＝2.2×10^-4，Q×f＝17822GHz，τ_εThe dielectric constant temperature coefficient is between-334 to-338 ppm/DEG C, compared with the prior literature report, the sintering temperature is greatly reduced, the lower dielectric loss is kept, and the dielectric constant temperature coefficient is more stable within the range of-55 to 85 ℃, so that the dielectric constant temperature coefficient is suitable for industrial application.

In conclusion, the dielectric material for the multilayer ceramic capacitor can meet the application requirements of the current radio frequency ceramic capacitor with the S2G temperature characteristic, has simple and controllable preparation process, low material dielectric loss and stable temperature coefficient of dielectric constant, can be co-fired with an Ag inner electrode (950 ℃), and can be widely applied to the radio frequency communication industry.

Claims

1. A dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor is characterized in that: comprises a ceramic material and a modifier;

The formula of the modifier is A₂CO₃-BO-C₂O₃-SiO₂(42:12:36:10 wt.%), wherein A is₂CO₃From 16 wt.% Na₂CO₃And 26 wt.% of Li₂CO₃Forming; BO consists of 4 wt.% MgO with 8 wt.% CuO; c₂O₃From 32 wt.% of B₂O₃And 4 wt.% of Nd₂O₃Forming;

the formulation of the dielectric material for the multilayer ceramic capacitor is Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂+ x wt.% of modifier, wherein x is in the value range of 1 to 2; prepared by a solid phase method, and the main crystal phase of the crystal is rutile type Mg_0.17Nb_0.33Ti_0.5O₂The structure, the sintering temperature is 850-900 ℃; a dielectric constant of 58 to 71 and a dielectric loss of 2X 10^-4～5×10^-4The Q x f value is 8000-18000 GHz, the temperature coefficient of dielectric constant is stable and satisfies the S2G temperature characteristic.

2. The dielectric material for low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitors as claimed in claim 1, wherein: when x is 1, the dielectric constant of the material at the sintering temperature of 900 ℃ is 70.6, and the dielectric loss is as low as 2.2 multiplied by 10^-4The Q x f value of the quality factor is as high as 17822 GHz.

3. The method for preparing a dielectric material for a low-temperature sintered Mg-Ti-Nb multilayer ceramic capacitor as claimed in claim 1, wherein: the method comprises the following steps:

step 1, adding MgO and TiO₂、Nb₂O₅、V₂O₅And Ta₂O₅According to the chemical formula Mg _0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂Burdening is carried out;

step 2: putting the powder prepared in the step 1 into a ball milling tank, performing planetary ball milling for 4-6 hours according to the mass ratio of the powder to zirconium balls to deionized water of 1: 5-7: 3-5, drying the mixed slurry in an oven after the ball milling is finished, and then sieving by using a 40-100-mesh sieve; presintering the sieved powder in an atmosphere at 900-1100 ℃ for 3-5 hours;

step 4, modifying the modifier obtained in the step 3 according to Mg_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂+ x wt.% modifier, Mg added in step 2_0.17(Nb_0.32V_0.08Ta_0.6)_0.33Ti_0.5O₂In the pre-sintering material, the value range of x in the modifier is more than or equal to 1 and less than or equal to 2; and again according to the powder: zirconium ball: carrying out planetary ball milling for 3-5 hours at the mass ratio of deionized water of 1: 5-7: 3-5, and after drying ball milling materials, adding a polyvinyl alcohol solution into powder in the ball milling materials for bonding granulation;