RU2455235C1 - Method of producing tin hypothiophosphate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in production of piezoelectric ceramic materials. To obtain tin hypothiophosphate, tin chloride, phosphorus sulphide and sodium sulphide solutions are mixed in stoichiometric ratios. Each of the said starting components is dissolved in an organic solvent until a saturated solution is obtained, followed by ultrasonic treatment. The obtained mixture is settled until appearance of a brown precipitate of tin hypothiophosphate. The solvent is removed and the precipitate is washed on a filter with an organic solvent until negative reaction on the chloride ion. The obtained end product is dried and ground in a ball mill.

EFFECT: invention increases purity of the product, increases efficiency and eliminates explosion-hazard when producing tin hypothiophosphate.

5 cl, 4 tbl, 1 ex

Description

The invention relates to piezoelectric materials, in particular to a method for producing powders of the composition Me-P-S, intended for the production of piezoelectric ceramic films with a thickness of 2-10 microns, obtained by thermal spraying in vacuum.

Ferroelectric films based on tin hypothiophosphate Sn ₂ P ₂ S ₆ have high values of relative permittivity ε ^T ₃₃ / ε ₀ = 400 and piezoelectric sensitivity γ = 5.5-5.7 * 10 ^-7 V / Pa at low frequencies with volume excitation , which makes them promising for use in electro-acoustic devices.

The electrophysical properties of materials based on the hypothiophosphate phases of Me-PS systems, in particular, on the basis of Sn ₂ P ₂ S ₆ and its analogues, are presented in the articles: Burcha D.M., Voroshilov Yu.V., Slivka V.Yu., Turyanitsa I .D. Complex chalcogenides and chalcogen halides (production and properties). Kiev: Vishcha school, 1983. P.180 [1], Gerzanich E.I., Fridkin V.M. Ferroelectrics type A ^V B ^VI C ^VII . M .: Nauka, 1982. P.357 [2], Belyaev L.M., Grekov A.A., Zaks P.L., Tatarenko L.N. // Acoustic journal. 1977.V.23. No. 5. P.810 [3], Merz V.I., Nietzsche R. // Izv. USSR Academy of Sciences. Ser. Fiz. 1964. V. 28, No. 4. P.681 [4], Vysochansky Yu.M., Cream V.Yu. // Izv. USSR Academy of Sciences. Ser. physical 1987.V. 51. No. 12. S.2156 [5]. Materials based on metal hypothiophosphates have not found practical application due to the complexity and harmfulness of their preparation. Tin (II) hypothiophosphate has record-high values of volumetric piezoelectric characteristics among known single-phase ferroelectric materials, and piezoelectric sensors made on its basis can convert comprehensive compression into an electrical signal with high efficiency. Due to this, alkali metal hypothiophosphates - Me ₄ P ₂ S ₆ (Me = Li, Na, K) - are of particular interest for use in piezotechnics. They can be used to obtain hypothiophosphates of divalent metals as a starting reagent (precursor) in the exchange interaction (Jandali MZ, Eulenberger G., Hahn H. // Z. anorg. Allgem. Chem. 1980. V. 470. No. 11. S .39 [6]) in solutions with salts of these metals according to the schematic reaction:

Currently known methods for producing hypothiophosphate phases, including alkali metal hypothiophosphates, have several disadvantages. In practice, the most commonly used synthesis of these phases is from simple substances of Me-P-S ternary systems, binary compounds formed in Me-P, Me-S and P-S binary systems, as well as from various combinations of these simple substances and binary compounds. To prevent chemical interaction with water vapor and oxygen, the process is carried out in sealed ampoules. The syntheses are carried out at temperatures from 350 ° C for As ₂ P ₂ S ₇ (Wibbelmann C., Brockner W. // Z. Naturforsch. A. 1981. B.36. No. 8. S.836 [8]), up to 950 ° C for GdPS ₄ (Rolland Le, Molinie P., Cdombet P. // Cr Acad. Sci. Ser 2 1990. Vol.310. No. 9. P.1201 [9]), and the duration of the processes is from two days for Sn ₂ P ₂ S ₆ (Carpentier CD, Nitsche R. // Mater. Res. Bull. 1974. Vol.9. No. 4. P.401 [10]), up to three months for Co ₂ P ₂ S ₆ , Ni ₂ P ₂ S ₆ , Mg ₂ P ₂ S ₂ (Klingen W., Ott R., Hahn H. // Z. anorg. Allgem. Chem. 1973. B.396. No. 3. S.271 [11 ]).

However, the use of low-melting, volatile and harmful components (sulfur, phosphorus, phosphorus sulfides) in a closed volume due to increased pressure in the ampoule often leads to its rupture. To avoid this, an extremely slow increase in temperature and the creation of a temperature gradient along the ampoule are used - polytemperature synthesis, which, however, does not completely eliminate the explosion hazard. A disadvantage of the known methods is also the volume of synthesized substances limited by the ampoule, which reduces productivity.

The closest synthesis method to the claimed object is a laboratory method of high-temperature synthesis of tin hypothiophosphate in unsealed semi-closed ampoules having a capillary hole for partial vapor release (RU 2089491, 6 IPC C01B 25/00, publ. 09/10/1997 [12]), accepted for the prototype.

The target product is obtained by reacting stoichiometric amounts of metal, phosphorus and sulfur compounds in air in two stages with exposure at a temperature of 350-450 ° C in the case of InPS ₄ and 450-550 ° C in the case of Sn ₂ P ₂ S ₆ for 20-30 min at each stage with intermediate cooling to room temperature and grinding the product. Oxides SnO and In ₂ O ₃ are used as initial metal compounds, and its sulfide P ₄ S ₁₀ is used as phosphorus compounds. The low-melting phosphorus sulfide and sulfur form a liquid phase, which interacts with solid tin oxide to form hypothiophosphate. The yield of the product, according to the authors, was approximately 98% of the theoretically possible. The total interaction time of the starting components is 40-60 minutes. Preparation of the initial charge, heating the furnace to the required temperature, grinding of the sintered mass obtained after heating take more than one hour. The synthesis process of one sample takes a total of more than two hours.

The disadvantages of the prototype method are as follows:

- due to the easy oxidizability of the precursors and synthesis products, there remains the danger of contamination of the target products with oxygen-containing compounds at intermediate stages of the process, which leads to a decrease in the yield of the pure product, and there is no information about the purity of the target product;

- the need to use special refractory ampoules;

- the duration of the process of preparation of tin hypothiophosphate in a limited volume of the ampoule, which is more than 2 hours, which reduces the productivity of the method.

Due to these drawbacks, the known method has not found industrial application.

The objective of the present invention is to develop a low-temperature, explosion-proof method for producing tin hypothiophosphate, eliminating the above disadvantages and feasible in industrial production.

The technical result of the claimed invention is to increase the purity of the target product by eliminating the oxidation of precursors and synthesis products, increasing the productivity of the method by reducing the synthesis time of a large volume of tin hypothiophosphate to 2-5 minutes, eliminating the explosiveness of the method by eliminating high-temperature synthesis.

The specified technical result is achieved in that the method for producing tin hypothiophosphate consists in synthesizing the target product from a system of starting components, including tin (II) compounds and phosphorus sulfides taken in stoichiometric ratios, and grinding the synthesized product.

According to the invention, sodium sulfide is introduced into the system of starting components, and tin chloride SnCl _{2 is} used as the tin (II) compound. Each source component is dissolved in an organic solvent until a saturated solution is obtained, followed by sonication, the resulting solutions are mixed, sedimented until a brown precipitate of tin hypothiophosphate appears, the solvent is removed, the precipitate is washed on the filter with an organic solvent until a negative reaction to the chloride ion is obtained, and the obtained target product is dried.

In special cases, the execution of the method:

- ethanol is used as an organic solvent;

- acetone is used as an organic solvent;

- toluene is used as an organic solvent;

- solutions of the starting components are treated with ultrasound with a power of 60-240 W for 20 minutes at a temperature below the boiling point of the solvent.

The simultaneous interaction of sodium sulfide, phosphorus sulfide and tin chloride in an organic solvent causes the chemical reaction of sodium hypothiophosphate formation: 4Na ₂ S + P ₄ S ₈ → 2Na ₄ P ₂ S ₆ , which represents an intermediate stage of the process. In this case, the alkaline metal cation Na ⁺ is exchanged for the divalent tin cation Sn ²⁺ by the reaction 2Na ₄ P ₂ S ₆ + 4SnCl ₂ → 2Sn ₂ P ₂ S ₆ + 8NaCl and the synthesis of tin hypothiophosphate occurs at the moment of the appearance of the active state of sodium hypothiophosphate, which is characterized by the absence of crystallization. The results of the authors' studies confirm the absence of interaction of SnCl ₂ with Na ₄ P ₂ S ₆ single crystals in ethanol solution. Ultrasonic treatment of these solutions increases the diffusion rate of components in an organic solvent, which accelerates the formation of the target product.

Table 1 shows the comparative characteristics of the organic solvents used in the present method.

Table 2 shows the solubility data of Na ₂ S, P ₄ S ₈ , SnCl ₂ in ethanol, acetone, toluene.

Table 3 shows the comparative values of the 2θ angles and Int-f intensities presented by the ICSD database (No. 039232), and the 2θ angles and Int-f intensities of the X-ray diffraction analysis of tin hypothiophosphate Sn ₂ P ₂ S ₆ obtained by the exchange interaction in ethanol using the hypothiophosphate phase sodium Na ₄ P ₂ S ₆ at the time of its formation.

Table 4 shows the comparative electrophysical characteristics of thin h = 2-10 μm films of tin hypothiophosphate synthesized by the prototype method and the claimed method.

A method of obtaining tin hypothiophosphate is as follows. Prepare a portion of sodium sulfide Na ₂ S grade b.p., phosphorus sulfide P ₄ S ₈ , which is a mixture of P ₄ S ₇ and P ₄ S ₉ and tin chloride SnCl ₂ grade b.a. in a stoichiometric ratio calculated by the reaction equation:

4Na ₂ S + P ₄ S ₈ + 4SnCl ₂ → 2Sn ₂ P ₂ S ₆ + 8NaCl,

in the amount of wt.%: Na ₂ S - 21.2%, P ₄ S ₈ - 26.1%, SnCl ₂ - 52.7%. Each sample was dissolved in ethanol until saturated solutions were obtained, they were sonicated, poured into one glass, sedimented until a brown precipitate of tin hypothiophosphate appeared, the solvent was removed, the precipitate was washed on the filter with an organic solvent until a negative reaction to the chloride ion was obtained, and the obtained target product was dried. Then crushed in a ball mill to obtain a powder fineness of 2-5 microns.

The choice of organic solvents is due to the fact that precursors dissolve in different ways in solvents (table 1), characterized by different polarities. Solvents with a high polarity dissolve sodium sulfide better, and with a low - phosphorus sulfide.

Knowledge of the solubility of the starting components in various solvents (Table 2) allows us to calculate the ratio of the starting components and the solvent in mol% to obtain a saturated solution. The choice of ethanol as a solvent is due to the fact that the solubility of precursors: sodium sulfide, phosphorus sulfides, tin chloride, is higher than that of acetone and toluene, this allows to obtain a larger amount of the target product with a smaller amount of solvent.

Example

0.31 g of sodium sulfide powder (0.004 mol) is dissolved in 119.2 ml of ethanol. In another container, 0.38 g of phosphorus sulfide (0.001 mol) is added to 47.5 ml of ethanol. 0.77 g (0.004 mol) of tin chloride in 14.9 ml of ethanol are dissolved in a third beaker. The ratio of the starting component and the solvent provides saturated solutions, the solubility of sodium sulfide in ethanol is 0.003 g / ml, the solubility of phosphorus sulfide in ethanol is 0.008 g / ml, the solubility of tin chloride in ethanol is 0.052 g / ml. Then the glasses with the solutions were placed in an ultrasonic sink of the Elmasonik S30H brand with a power of 60-240 W and treated with ultrasound for 20 minutes at a temperature of 45 ° C, below the boiling point of the solvent. The treated solutions were poured into one glass, settled until a brown precipitate of tin hypothiophosphate appeared, the solvent was removed, the precipitate was washed on the filter with a minimum volume of organic solvent until a negative reaction to the chloride ion was obtained, and the obtained target product was dried. 0.88 g (88%) of tin hypothiophosphate was obtained as a brown powder.

In a glass containing a mixture of the starting components in ethanol, a chemical reaction of the form occurs:

4Na ₂ S + P ₄ S ₈ + 4SnCl ₂ → 2Sn ₂ P ₂ S ₆ + 8NaCl.

To confirm the formation of the Sn ₂ P ₂ S ₆ phase, X-ray phase and elemental analyzes of the obtained compound were carried out. The phase composition of Sn ₂ P ₂ S _{6 was} determined by X-ray phase analysis (XRD) on a DRON-2.0 diffractometer with copper radiation (λ = 1.54 Å). As follows from Table 3, the values of the 2θ angles and the Int-f intensities of the tin hypothiophosphate Sn ₂ P ₂ S ₆ obtained by the exchange interaction in ethanol using the phase of sodium hypothiophosphate Na ₄ P ₂ S ₆ at the moment of its formation, and the 2θ angles and the Int-f intensities represented by the ICSD database (No. 039232) are practically the same. This indicates the identification of the tin hypothiophosphate phase and the presence of a negligible amount of tin sulfide impurity (2θ = 22.7, Int-f = 347).

To justify the practical importance of using tin hypothiophosphate synthesized by the claimed method, thin films with a thickness of h ~ 2-10 μm were applied to a round aluminum substrate with a diameter of 30 mm by thermal spraying in vacuum. The films were polarized at room temperature in a pulsed mode at a voltage of 100-200 V per mm of sample thickness for 30 seconds. The relative permittivity ε ^T ₃₃ / ε ₀ was measured using an E-84 alternating current bridge at a frequency of 1000 Hz. The piezosensitivity of the γ samples to sound pressure was measured at a frequency of 70 Hz on a special stand including a sound chamber in which the corresponding sound pressure was generated, as well as using a master sound generator and a highly sensitive V7-40 millivoltmeter. As follows from Table 4, the relative dielectric constant ε ^t ₃₃ / ε ₀ = 350-400 and the piezoelectric sensitivity γ of the piezoelectric Sn ₂ P ₂ S ₆ films at low frequencies with volume excitation is 5.5-5.7 * 10 ^-7 V / Pa.

The obtained piezoelectric characteristics indicate the possibility of using the synthesized product for spraying films that are not inferior in properties to the films obtained from Sn ₂ P ₂ S ₆ synthesized in vacuum ampoules from simple substances (Rogach E.D., Protsenko N.P., Savchenko E.A., Sandzhiev D.N., Kryshtop V.T. // Proceedings of the Academy of Sciences of the USSR, Ser.Phys.

Information sources

1. Birch D.M., Voroshilov Yu.V., Cream V.Yu., Turyanitsa I.D. Complex chalcogenides and chalcogen halides (production and properties). Kiev: Vishcha school, 1983. P.180.

2. Gerzanich E.I., Fridkin V.M. Ferroelectrics type A ^V B ^VI C ^VII . M .: Nauka, 1982. P.357.

3. Belyaev L. M., Grekov A. A., Sachs P. L., Tatarenko L. N. // Acoustic journal. 1977.V.23. No. 5. S.810.

4. Merz V.I., Nietzsche R. // Izv. USSR Academy of Sciences. Ser. Fiz. 1964. V. 28, No. 4. S.681.

5. Vysochansky Yu.M., Cream V.Yu. // Izv. USSR Academy of Sciences. Ser. physical 1987.V. 51. No. 12. S.2156.

6. Jandali M.Z., Eulenberger G., Hahn H. // Z. anorg. allgem. Chem. 1980. B.470. No. 11. S.39.

7. Rybina I.H. Abstract. dis ... cand. tech. sciences. Rostov-on-Don, 1997.25 p.

8. Wibbelmann C., Brockner W. // Z. Naturforsch. A. 1981. B.36. No. 8. S.836.

9. Rolland Le, Molinie P., Cdombet P. // C.r. Acad. Sci. Ser 2 1990. Vol. 310. No. 9. P.1201.

10. Carpentier C. D., Nitsche R. // Mater. Res. Bull. 1974. Vol. 9. Number 4. P.401.

11. Klingen W., Ott R., Hahn H. // Z. anorg. allgem. Chem. 1973. B.396. Number 3. S.271.

12. RU 2089491, 6 IPC C01B 25/00, Method for the production of tin hypothiophosphate. - prototype.

13. Rogach E.D., Protsenko N.P., Savchenko E.A., Sandzhiev D.N., Kryshtop V.T. // Izv. USSR Academy of Sciences. Ser. physical 1987.V. 51. No. 12. S.2269.

Table 1 Comparative characteristics of organic solvents used in the claimed method General properties ethanol acetone toluene Molecular formula C ₂ H ₅ (OH) C ₃ H ₆ O C ₆ H ₅ -CH ₃ Molar mass, g / mol 46,069 58.08 92.14 Appearance colorless liquid colorless odorless liquid pungent colorless volatile liquid Density, kg / ml at 20 ° C 789.3 789.9 866.94 Solubility in water, g / 100 ml completely soluble completely miscible with water 0,053 Melting temperature -114.3 ° C (158.8 K) -95 ° C (178 K) -95 ° C (178 K) Boiling temperature 78.4 ° C (351.6 K) 56.1 ° C (329.1 K) 110.6 ° C (383.6 K) pKa 15.9 twenty 35 Viscosity, cP at 20 ° C 1,2 2.95 2.95 Surface tension, · 10 ^-3 N / m at 20 ° C 22.39 23.7 23.7 Dipole moment, D 1,69 2.84 0.37

table 2 Solubility of Na ₂ S, P ₄ S ₈ , SnCl ₂ in ethanol, acetone, toluene Solubility Na ₂ S P ₄ S ₈ SnCl ₂ mol / l g / ml mol / l g / ml mol / l g / ml alcohol 3.3E-02 2.6E-03 2,1E-02 8,0E-03 2.7E-01 5.16E-02 acetone 3,1E-02 2,4E-03 1,4E-02 5,4E-03 2,0E-01 4.0E-02 toluene 2.6E-03 2,0E-04 5,3E-04 2,0E-04 5,3E-03 1,0E-03

Table 3 Comparative values of 2θ angles and Int-f intensities represented by the ICSD database (No. 039232), and 2θ angles and Int-f intensities of X-ray diffraction analysis of tin hypothiophosphate Sn ₂ P ₂ S ₆ obtained by the exchange interaction in ethanol using the sodium hypothiophosphate phase Na ₄ P ₂ S ₆ at the time of its formation ICSD No. 039232 experiment ICSD No. 039232 experiment 2θ Int-f 2θ Int-f 2θ Int-f 2θ Int-f 15.1 178 15,5 112 33,4 221 33.5 154 16,4 232 16.6 124 33.8 616 33.9 412 16.7 38 16.8 fifteen 34.2 360 34.7 325,4 18.1 247 eighteen 124 35.3 99 35,2 56 18.9 462 18.7 289 35.9 168 35.9 68.5 20.3 440 20.3 311.1 36.5 thirty 36.6 17.9 20.5 770 20.5 328,2 37,4 321 37.3 212 22.3 63 21.8 23 37.7 457 37.8 300 22.7 347 38 238 38 one hundred 23.7 19 23.5 24 38,4 294 38.1 196 25.6 999 25.5 999 38.6 364 38.5 324 26.1 193 26.3 159.8 39.8 57 39.7 38 26.5 247 26.7 190 39.9 117 39.9 56 27.4 342 27.3 228 40,2 22 40.1 fourteen 27.5 256 27.5 196 40.3 24 40.3 10 29th 73 28.7 48 41,4 21 41.3 fourteen 29.2 65 29.2 28.5 42,2 fifteen 42.3 10 30.5 196 30,2 130 42,4 84 42.5 53 31 twenty 31 10 42.6 56 42.8 25 31,2 169 31,2 fifteen 43 47 43 fifteen 31.6 323 31.5 221 43,2 114 43,2 87 32 fourteen 32.1 23.9 43,4 175 43,4 115 33.1 292 33.1 123

Table 4 Comparative electrophysical characteristics of thin (h ~ 2-10 μm) films of tin hypothiophosphate synthesized by the prototype method and the claimed method Electrophysical characteristics Piezoelectric films of tin hypothiophosphate synthesized prototype method the claimed method ε ^t ₃₃ / ε ₀ 360-400 350-400 γ * 10 ^-7 V / Pa 5.6-6.0 5.5-5.7

Claims (5)

1. The method of producing tin hypothiophosphate, which consists in the synthesis of the target product from a system of starting components, including tin (II) compounds and phosphorus sulfides, taken in stoichiometric ratios, and grinding the synthesized product, characterized in that sodium sulfide is introduced into the system of starting components, and as tin compounds (II) used tin chloride SnCl _2, each of the source component is dissolved in an organic solvent to obtain a saturated solution, followed by sonication are mixed Acquiring solutions, settled until the brown precipitate of tin gipotiofosfata, the solvent was removed and the precipitate was washed on the filter with an organic solvent until a negative reaction for chloride ions, and the resulting title product is dried. 2. The method according to claim 1, characterized in that ethanol is used as an organic solvent. 3. The method according to claim 1, characterized in that acetone is used as an organic solvent. 4. The method according to claim 1, characterized in that toluene is used as an organic solvent. 5. The method according to claim 1, characterized in that the solutions of the starting components are treated with ultrasound with a power of 60-240 W for 20 minutes at a temperature below the boiling point of the solvent.