CN112064106B - Method for preparing strontium dipotassium cyclic phosphate crystal and application - Google Patents

Abstract

The application discloses a method for preparing strontium dipotassium cyclophosphate crystal and application thereof. The method comprises the following steps: the strontium dipotassium phosphate crystal is prepared by a fluxing agent method, which comprises the step of adding K₂SrP₄O₁₂Growing a mixture of polycrystal and fluxing agent to obtain the strontium dipotassium cyclophosphate crystal; the fluxing agent is prepared from a potassium source I and a phosphorus source I. The cyclic dipotassium strontium phosphate (K) prepared by the method₂SrP₄O₁₂) The crystal has moderate nonlinear optical coefficient, ultraviolet cut-off edge less than 200nm, no deliquescence and moderate growth temperature, and is a potential deep ultraviolet nonlinear optical crystal.

Description

Method for preparing strontium dipotassium cyclic phosphate crystal and application

Technical Field

The application relates to a method for preparing strontium dipotassium cyclophosphate crystals and application thereof, belonging to the technical field of photoelectron functional materials.

Background

In recent years, with the rapid development of laser technology, it is widely used in many fields such as optics, communication, medicine, military and the like, and especially, an all-solid-state laser is receiving attention due to its advantages such as small volume, low price and simple structure. The current solid-state laser can not generate laser light with the wavelength of below 400nm, and the frequency conversion crystal, namely the nonlinear optical crystal, is required to generate the laser light with the wavelength of 400 nm. From the development of the existing nonlinear optical crystal material, in the ultraviolet spectral region (200-₂O₄)，LBO(LiB₃O₅) The output of ultraviolet laser can be realized. And in the deep ultraviolet region (<200nm), only KBBF (KBe) capable of outputting deep ultraviolet laser in direct frequency doubling mode₂BO₃F₂) And (4) crystals. However, KBBF has two disadvantages, the first: virulent BeO is used in the synthesis process; second, crystalCannot grow in the c direction. The two defects severely limit the application, so that the search for new deep ultraviolet nonlinear optical crystal materials becomes the leading edge and the hot spot of the research field of nonlinear optical crystal materials.

Disclosure of Invention

According to one aspect of the application, a method for preparing a crystal of strontium dipotassium cyclic phosphate is provided, and the obtained crystal of strontium dipotassium cyclic phosphate (K) of the deep ultraviolet nonlinear optical crystal is prepared by the method₂SrP₄O₁₂) The crystal has moderate nonlinear optical coefficient, ultraviolet cut-off edge of less than 200nm, no deliquescence and moderate growth temperature, and is a potential deep ultraviolet nonlinear optical crystal.

A method for preparing strontium dipotassium cyclophosphate crystal, which is prepared by adopting a fluxing agent method, comprises

Will contain K₂SrP₄O₁₂Growing a mixture of polycrystal and fluxing agent to obtain the strontium dipotassium cyclophosphate crystal;

the fluxing agent is prepared from a potassium source I and a phosphorus source I.

Specifically, the strontium dipotassium cyclophosphate crystal is a nonlinear optical crystal material.

Alternatively, the potassium source I is selected from potassium-containing compounds;

the potassium-containing compound is any one of potassium carbonate, monopotassium phosphate and potassium nitrate.

The phosphorus source I is selected from compounds containing phosphorus,

the phosphorus-containing compound is selected from ammonium dihydrogen phosphate and phosphoric acid.

Preferably, the fluxing agent consists of K₂CO₃And NH₄H₂PO₄And (4) preparing.

Alternatively, the molar ratio of the potassium source I to the phosphorus source I is 1: 2-4; wherein the mole number of the potassium source I is calculated by the mole number of the potassium source I; the mole number of the phosphorus source I is calculated by the mole number of the phosphorus source I.

Preferably, the molar ratio of the potassium source I to the phosphorus source I is 1: 3.

optionally, the preparation method of the fluxing agent comprises: and heating the materials containing the potassium source I and the phosphorus source I to 450-550 ℃, and synthesizing at constant temperature for 45-55 h to obtain the fluxing agent.

Optionally, the growing conditions include:

will contain K₂SrP₄O₁₂Uniformly mixing the polycrystal and the fluxing agent, cooling to 750-850 ℃ at the speed of 80-120 ℃/h, and then cooling at the speed of 1.5-2.5 ℃/h to obtain the strontium dipotassium cyclic phosphate crystal.

Optionally, the mixing comprises: the raw materials are subjected to heat preservation for 15-25 h at the temperature of 850-950 ℃.

Specifically, the method comprises the following steps: will contain K₂SrP₄O₁₂Heating the raw materials of the polycrystal and the fluxing agent to 850-950 ℃, preserving the heat for 15-25 h, then cooling to 750-850 ℃ at the speed of 80-120 ℃/h, and then cooling at the speed of 1.5-2.5 ℃/h until crystals are separated out from the liquid surface, thus obtaining the strontium dipotassium cyclic phosphate crystal.

In one possible embodiment, the main growth conditions of the strontium dipotassium cyclic phosphate crystal are as follows, the growth container is a platinum crucible, and the synthesized K₂SrP₄O₁₂Uniformly mixing the polycrystalline raw material and the fluxing agent in a molar ratio of 1: 1-5, transferring the mixture into a platinum crucible, placing the platinum crucible into a programmed temperature control furnace, heating to 850-950 ℃ for melting, and keeping the temperature for 15-25 hours. After the materials are uniformly mixed, rapidly cooling to 750-850 ℃ at the speed of 80-120 ℃/h, then cooling at the speed of 1.5-2.5 ℃/h until tetragonal prismatic crystals are separated out on the liquid surface, turning off a power supply, and naturally cooling to room temperature to obtain a plurality of K particles₂SrP₄O₁₂A single crystal.

Alternatively, K₂SrP₄O₁₂The manner of obtaining polycrystals includes:

heating materials containing a strontium source, a potassium source II and a phosphorus source II to 550-650 ℃, and synthesizing at constant temperature for 45-55 h to obtain K₂SrP₄O₁₂And (4) polycrystallization.

Preferably, will contain SrCO₃、K₂CO₃(or KH)₂PO₄) And NH₄H₂PO₄Heating the raw materials to 550-650 ℃, and synthesizing at constant temperature for 45-55 h to obtain K₂SrP₄O₁₂And (4) polycrystallization.

Specifically, SrCO is to be contained₃、K₂CO₃(or KH)₂PO₄) And NH₄H₂PO₄The temperature of the raw materials is raised to 200-240 ℃ at a heating rate of 80-120 ℃, the temperature is kept constant at 200-240 ℃ for 22-26 hours, then the temperature is raised to 550-650 ℃ at a rate of 28-32 ℃/h, the temperature is kept constant for 45-55 hours, and K is obtained₂SrP₄O₁₂And (4) polycrystallization.

In the present application, according to formula K₂SrP₄O₁₂And accurately weighing the raw materials according to the molar ratio of each substance in the molecular formula to prepare the polycrystal.

Optionally, the strontium source is selected from strontium containing compounds; the strontium-containing compound is selected from any one of strontium carbonate and strontium nitrate.

The potassium source II is selected from compounds containing potassium; the potassium-containing compound is any one of potassium carbonate, monopotassium phosphate and potassium nitrate.

The phosphorus source II is selected from a phosphorus-containing compound, and the phosphorus-containing compound is selected from any one of ammonium dihydrogen phosphate and phosphoric acid.

Preferably, the potassium source I and the potassium source II are the same substance, and the phosphorus source I and the phosphorus source II are the same substance.

Alternatively, the K₂SrP₄O₁₂The molar ratio of polycrystal to flux is 1:1 to 5.

Optionally, the preparation method of the strontium dipotassium cyclic phosphate crystal at least comprises the following steps:

a) obtaining K₂SrP₄O₁₂Polycrystal;

b) preparing the fluxing agent by using a potassium source I and a phosphorus source I;

c) will contain K₂SrP₄O₁₂And heating and cooling the mixture of the polycrystal and the fluxing agent to obtain the strontium dipotassium cyclic phosphate crystal.

The following describes a preferred method for preparing strontium dipotassium cyclic phosphate crystals:

(1) the initial raw material is SrCO₃、K₂CO₃(or KH)₂PO₄) And NH₄H₂PO₄According to the formula K₂SrP₄O₁₂Accurately weighing the raw materials according to the molar ratio of the raw materials, grinding and uniformly mixing the raw materials in a mortar, and pressing the raw materials into lump materials;

(2) putting the block material into a corundum cup, heating to 600 ℃ in a muffle furnace, and synthesizing for 50 hours at constant temperature to obtain K₂SrP₄O₁₂Polycrystalline raw materials;

(3) weighing K according to the molar ratio of 1:3₂CO₃And NH₄H₂PO₄Grinding and uniformly mixing the raw materials in a mortar, placing the raw materials in a platinum crucible, heating the mixture to 500 ℃ in a muffle furnace, and synthesizing the mixture for 50 hours at constant temperature to obtain a fluxing agent required by growth;

(4) k obtained in the steps (2) and (3) respectively₂SrP₄O₁₂Uniformly mixing a polycrystalline raw material and a fluxing agent according to a molar ratio of 1: 1-5, placing the mixture in a platinum crucible, heating to 900 ℃, and keeping the temperature for 20 hours to uniformly mix the mixture;

(5) rapidly cooling to 800 ℃, then cooling at the rate of 2 ℃ per hour until tetragonal prismatic crystals are separated out on the liquid surface, turning off a power supply, and naturally cooling to room temperature to obtain the monocrystal.

The specific chemical reaction formula is as follows:

K₂CO₃+SrCO₃+4NH₄H₂PO₄＝K₂SrP₄O₁₂+2CO₂↑+4NH₃↑+6H₂O↑

or SrCO₃+2KH₂PO₄+2NH₄H₂PO₄＝K₂SrP₄O₁₂+CO₂↑+2NH₃↑+5H₂O↑

According to another aspect of the application, a strontium dipotassium cyclic phosphate crystal is provided, and the strontium dipotassium cyclic phosphate crystal is prepared according to the method of any one of the above methods;

the molecular formula of the strontium dipotassium cyclic phosphate crystal is K₂SrP₄O₁₂Belongs to the tetragonal system, space group I-4.

The crystal material of the strontium dipotassium cyclo-phosphate is a monocrystal material, and the structure of the crystal material contains [ P ]₄O₁₂]^4-Eight-membered ring, the crystal has second order nonlinear optical effect.

K₂SrP₄O₁₂The size of the single crystal is 3-5 mm.

In another aspect of the application, the crystal of strontium dipotassium cyclophosphate prepared by the method is applied to a laser frequency conversion device.

The beneficial effects that this application can produce include:

1) the application aims to find a novel preparation method of a deep ultraviolet nonlinear optical crystal. Various tests show that the cyclic dipotassium strontium phosphate (K) prepared by the method of the application₂SrP₄O₁₂) Has moderate nonlinear optical coefficient, ultraviolet cut-off edge less than 200nm, no deliquescence and moderate growth temperature, and is a potential deep ultraviolet nonlinear optical crystal.

2) In the application, a fluxing agent method is adopted to prepare strontium dipotassium phosphate crystal with the molar ratio of K being 1:3₂CO₃:NH₄H₂PO₄Obtaining millimeter-sized K in flux₂SrP₄O₁₂A single crystal. The second-order nonlinear coefficient of the crystal is 0.5 times of that of KDP single crystal, the ultraviolet cut-off edge is less than 200nm, the class-1 phase matching can be realized, and the crystal is a potential deep ultraviolet nonlinear optical crystal material.

3) The method for preparing the strontium dipotassium cyclic phosphate crystal has the advantages of cheap and easily available raw materials, low crystal growth temperature and the like.

Drawings

FIG. 1 is a photograph of a crystal obtained by measurement in one embodiment of the present application, in which 1 cell represents 1 mm;

FIG. 2 is a graph of frequency doubling intensity as a function of particle size for a KSPO polycrystalline powder according to one embodiment of the present application;

FIG. 3 is a graph of the diffuse reflectance of UV-Vis-NIR measured for KSPO crystals in one embodiment of the present application;

FIG. 4 is a plot of the band of KSPO crystals obtained in one embodiment of the present application after conversion by a formula.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.

The purity of the raw materials used and the manufacturer are shown in table 1:

TABLE 1

Name of medicine	Purity of	Manufacturer of the product
			K2CO3	99.9％	Shanghai chemical reagent company of Chinese national drug group
KH2PO4	99.9％	Shanghai chemical reagent company of Chinese national drug group
			SrCO3	99.9％	Shanghai chemical reagent company of Chinese national drug group
NH4H2PO4	99.9％	Shanghai chemical reagent company of Chinese national drug group

In the present application, the crystal structure data was tested using a Rigaku Saturn724+ CCD model four-circle diffractometer with wavelength of Mo Ka rays

Carrying out data acquisition at room temperature;

the second-order nonlinear optical coefficient adopts' Nd for nonlinear material characteristic research: YAG laser experiment system' instrument test, fundamental wave wavelength is 1064 nm;

testing the diffuse reflection spectrum of the crystal by adopting a Perkin-Elmer Lambda 900 instrument;

EXAMPLE 1 preparation of crystals

Preparation of crystal synthesis of single crystal growth raw material: the synthesis is carried out by adopting a traditional high-temperature solid-phase synthesis method. The initial raw material is K₂CO₃、SrCO₃And NH₄H₂PO₄According to the formula K₂SrP₄O₁₂Accurately weighing the raw materials according to the molar ratio of each substance in the molecular formula, grinding and uniformly mixing the raw materials in a mortar, and pressing the raw materials into lump materials; putting the block material into a corundum cup, heating to 220 ℃ at a speed of 100 ℃/h in a muffle furnace, keeping the temperature at 220 ℃ for 24 hours, then heating to 600 ℃ at a speed of 30 ℃/h, keeping the temperature for 50 hours, grinding for 2-3 times in the constant temperature process (directly taking out the raw materials in the synthesis at high temperature without cooling, and after each grinding, putting the raw materials into the synthesis at 600 ℃ for synthesis), cooling, and taking out to obtain K₂SrP₄O₁₂Polycrystalline for crystal growth.

The crystal of strontium dipotassium cyclic phosphate belongs to a non-homoconstituent molten compound, and the growth of the crystal adopts a fluxing agent method. The fluxing agent is K₂CO₃And NH₄H₂PO₄Is prepared fromThe mixing molar ratio is K₂CO₃:NH₄H₂PO₄1: 3. Weighing K according to molar ratio₂CO₃And NH₄H₂PO₄Grinding and uniformly mixing the raw materials in a mortar, placing the raw materials in a platinum crucible, heating the mixture to 500 ℃ in a muffle furnace, and synthesizing the mixture for 50 hours at constant temperature to obtain the fluxing agent required by growth.

The main growth conditions of the strontium dipotassium cyclo-phosphate crystal are as follows: the growth container is a platinum crucible, and the synthesized K₂SrP₄O₁₂The polycrystalline raw material and the fluxing agent are uniformly mixed according to the molar ratio of 1:1, transferred into a platinum crucible, placed in a programmed temperature control furnace, heated to 900 ℃ for melting, and kept at the constant temperature for 20 hours. After the materials are uniformly mixed, the temperature is quickly reduced to 800 ℃ at a speed of 100 ℃/h, then the temperature is reduced at a speed of 2 ℃/h until tetragonal prismatic crystals are separated out on the liquid surface, the power supply is turned off, and the mixture is naturally cooled to room temperature, so that a plurality of particles with the size of 3-5 mmK are obtained₂SrP₄O₁₂Single crystals, as shown in figure 1.

EXAMPLE 2 preparation of crystals

The difference from the embodiment 1 is that: the initial raw material is KH₂PO₄、SrCO₃And NH₄H₂PO₄；

The synthesized K₂SrP₄O₁₂The polycrystalline raw material and the fluxing agent are uniformly mixed in a molar ratio of 1: 5.

Example 3 Performance testing

K grown in example 1₂SrP₄O₁₂The single crystal was subjected to diffraction data collection on a four-circle diffractometer, and the test data are shown in table 1. The analysis of the single crystal structure shows that the crystal is crystallized in the I-4 space group, and the unit cell parameter is

α＝β＝γ＝90o，

And Z is 2. Each asymmetric unit has one independent K, Sr and P atom and three independent O atoms.

TABLE 1K₂SrP₄O₁₂The crystallographic data and the structure of (a) are refined.

K obtained by solid phase synthesis₂SrP₄O₁₂The polycrystalline powder of (2) was screened for different particle sizes and tested on a powder frequency multiplier. As a result, it was found that the polycrystalline powders provided in the examples of the present application all had moderate intensity of frequency doubling response and the second-order nonlinear optical coefficient thereof was KDP (KH) which is a reference crystal₂PO₄) Around 0.5 times, and in addition, the doubling strength increases with increasing particle size, which indicates that it can achieve class I phase matching. The results of the test, which are typically represented by the polycrystalline powder prepared in example 1, are shown in FIG. 2, where FIG. 2 is a graph of KSPO doubling strength as a function of particle size. As can be seen in FIG. 2, KSPO (K)₂SrP₄O₁₂) The doubling intensity of the crystal is about half of KDP; in addition, the doubling intensity increases with the granularity, which shows that the I-type phase matching can be realized.

Growing the obtained K by a fluxing agent method₂SrP₄O₁₂The single crystals were ground to powder for testing the diffuse reflectance spectra, and the results show that K is provided herein₂SrP₄O₁₂The absorption edge of the single crystal is less than 200nm, and the band gap is more than 6.2 eV. Typically represented by the single crystal produced in example 1, FIG. 3 is a plot of the UV-Vis-NIR diffuse reflectance of KSPO crystals, and FIG. 4 is a plot of the band of KSPO crystals after conversion to the formula. As can be seen from FIGS. 3 and 4, the cut-off edge of the KSPO crystal in the ultraviolet region is less than 200nm, which means that the light transmission band can reach deep into the deep ultraviolet region.

The strontium dipotassium cyclic phosphate deep ultraviolet nonlinear optical crystal developed by the invention has moderate frequency doubling effect and short ultraviolet cut-off edge. In addition, the raw materials are cheap and easy to obtain, and a large single crystal can be obtained by a fluxing agent method. In conclusion, the crystal is a potential deep ultraviolet nonlinear optical crystal.

Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

Claims (4)

1. A method for preparing strontium dipotassium phosphate crystal is characterized in that the strontium dipotassium phosphate crystal is prepared by a fluxing agent method, and the method comprises the following steps:

will contain K₂SrP₄O₁₂Growing a mixture of polycrystal and fluxing agent to obtain the strontium dipotassium cyclophosphate crystal;

the fluxing agent is prepared from a potassium source I and a phosphorus source I;

the molar ratio of the potassium source I to the phosphorus source I is 1: 2-4;

wherein the mole number of the potassium source I is calculated by the mole number of the potassium source I;

the mole number of the phosphorus source I is calculated by the mole number of the phosphorus source I;

said K₂SrP₄O₁₂The molar ratio of polycrystal to flux is 1: 1-5;

the growth conditions include:

will contain K₂SrP₄O₁₂Uniformly mixing raw materials of the polycrystal and the fluxing agent, cooling to 750-850 ℃ at a speed of 80-120 ℃/h, and then cooling at a speed of 1.5-2.5 ℃/h to obtain the strontium dipotassium cyclic phosphate crystal;

the mixing comprises the following steps: the raw materials are subjected to heat preservation for 15-25 h at the temperature of 850-950 ℃.

2. The process of claim 1, wherein the potassium source I is selected from the group consisting of potassium-containing compounds,

the potassium-containing compound is any one of potassium carbonate, monopotassium phosphate and potassium nitrate;

the phosphorus source I is selected from compounds containing phosphorus,

the phosphorus-containing compound is selected from ammonium dihydrogen phosphate and phosphoric acid.

3. The method of claim 1, wherein the method of preparing the fluxing agent comprises: and heating the materials containing the potassium source I and the phosphorus source I to 450-550 ℃, and synthesizing at constant temperature for 45-55 h to obtain the fluxing agent.

4. The method of claim 1, wherein K is₂SrP₄O₁₂The manner of obtaining polycrystals includes:

heating materials containing a strontium source, a potassium source II and a phosphorus source II to 550-650 ℃, and synthesizing at constant temperature for 45-55 h to obtain K₂SrP₄O₁₂Polycrystal;

the strontium source is selected from strontium containing compounds; the strontium-containing compound is selected from any one of strontium carbonate and strontium nitrate;

the potassium source II is selected from compounds containing potassium; the potassium-containing compound is any one of potassium carbonate, monopotassium phosphate and potassium nitrate;

the phosphorus source II is selected from a phosphorus-containing compound, and the phosphorus-containing compound is selected from any one of ammonium dihydrogen phosphate and phosphoric acid.

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