UA70185C2 - process for preparation of titanium (ІV) thaLlium (І) tetrasulfide Тl₄ТіS₄ - Google Patents

Abstract

The invention relates to inorganic chemistry, in particular to methods for preparing complex ternary sulfides, which can be used as thermal electric materials. A process for preparation of titanium (ІV) tetrasulfide thallium (І) comprises stepped heating quartz vessels vacuum-processed to 0.13 Pa, which contain original components for synthesis: of elementary thallium, titanium and sulfur in necessary stoichiometric ratio to maximal temperature and keeping at this temperature for 24 hours and subsequent annealing at 650 К. Maximal temperature of synthesis is of 1073±5 К, and annealing lasts for 168 ±1 hours. The use of this invention allows to reduce duration of annealing and obtain phase uniform product.

Description

Description of the invention

The invention relates to the field of inorganic chemistry and inorganic materials science, in particular to methods 2 of obtaining complex ternary sulfides, individual representatives of which are promising thermoelectric materials with a high concentration of charge carriers and an optimal ratio of chemical bond components.

There is a known method of obtaining thallium(I)-titanium(M) tetrasulfide (TI ATi54), according to which the synthesis of TI ATiZd is carried out by the interaction of thallium(i) sulfide and titanium powder. Stoichiometric mixtures of these components were fused in vacuumed quartz ampoules and kept for several days at a temperature of 55°C.

After that, the temperature was gradually raised to 1100K, the samples were left at this temperature for a week and, finally, slowly cooled in the furnace. Small crystals of irregular habit were isolated from the reaction product for X-ray studies |1). The disadvantage of this method is its long duration and the need for preliminary synthesis of thallium sulfide (I!), which decomposes peritectically at 5OZK |21| and therefore technologically 729 it is difficult to obtain.

The closest to the proposed one is the synthesis of TI/TiZda, which was carried out by fusing the necessary amounts of thallium(I) sulfide with elemental titanium and sulfur in quartz ampoules vacuumed to 10-"Pa.

The maximum synthesis temperature was 1173K. Heating to the maximum temperature was carried out at a rate of 100 K/h. Alloys were annealed at 548K for 720 hours |Z). The disadvantages of this method are long annealing (720 hours) and the need for preliminary synthesis of thallium sulfide (1).

The invention is based on the task of obtaining a homogeneous thallium(I)-titanium(IM) tetrasulfide in a phase relationship using a simpler method.

The task is solved by the fact that it is implemented by a method that includes stepwise heating to the maximum temperature, holding at the same temperature for 24 hours and subsequent annealing at (650°C) in 29 quartz ampoules vacuumed to 0.13 Pa of the starting components, taken in the required stoichiometric (In the ratio, and differs in that elemental thallium, titanium and sulfur are used for synthesis, the maximum synthesis temperature is 1073-5K, and annealing lasts 168--1 hours.

The advantages over the prototype are a shorter annealing duration, exclusion from the process of synthesis of preliminary and obtaining binary components.

The method was carried out as follows. (heh)

Elemental thallium, titanium, and sulfur in a stoichiometric ratio were selected as starting components. -

The synthesis was carried out in quartz ampoules vacuumed to 0.13 Pa. In the course of the work, elementary components of the following purity were used: thallium of the TI-000 brand, sulfur Os. part 16-3, titanium iodide (99.99995 ХХБФЗ of the main component). Elemental thallium and sulfur were additionally purified. The oxide film on the surface of the waist was removed mechanically. The sulfur purification process consisted of vacuum melting, repeated vacuum distillation and subsequent pyrolysis. The temperature regime of TI/TIZ synthesis; (Fig. 1) consisted in stepwise heating of the reaction mixture to 1073-5K at a rate of 20K/hour. Temperature exposures were carried out for 24 hours at 40K above the melting temperature of 711255 (754K), at the boiling temperature of sulfur (923K) K and at the maximum synthesis temperature (1123K). Annealing was carried out at 65°C for 168-1 hours. w-v c The obtained product was investigated by the methods of differential thermal (DTA) and X-ray phase (XRF) analyses. The thermogram of the obtained product was characterized by only one endothermic effect at 783K, which corresponds to the melting of Ti/TiZ; and is in good agreement with literature data |Ж). The bar diagram of the obtained product, constructed on the basis of X-ray diffraction (Fig. 2) turned out to be identical to the diffraction pattern of TI ATizZ/ (Fig. 3) calculated on the basis of literature data |1) using the Rozhaegsei program! 2.3. -I Example 1. Additionally purified elemental initial components (thallium, titanium and sulfur) were taken in stoichiometric proportions, loaded into quartz ampoules, which were then vacuumed to 0.13Pa. o The temperature regime for the synthesis of TI/TiZd includes stepwise heating to 1070-1073K and holding at a temperature of -1073K, as well as further annealing at 650K for 200 hours. With the method of execution described above, where the 5-year annealing duration was increased by 32 hours, a result was obtained, similar to that obtained when the synthesis was performed with an annealing duration of 168 hours. Example 2. Additional purified elemental initial components (thallium, titanium and sulfur) were taken in stoichiometric proportions, loaded into quartz ampoules, which were then vacuumed to 0.13Pa.

The temperature regime for the synthesis of TI/TiZd includes stepwise heating to 1070-1073K and holding at a temperature of 1073K, as well as further annealing at 650K for 120 hours. With the method of execution described above, where the duration of annealing was reduced by 48 hours, the homogeneity of the synthesis product was not achieved, which (Ф) is confirmed by the data of X-ray phase analysis, on the basis of which the bar diagram ko was constructed (Fig. 4), the comparison of which with the diffractogram, calculated on the basis of literature data (Fig. 3) and confirmed the heterogeneity of the synthesis product. So, as examples 1 and 2 show, in which the annealing time during synthesis varies, the selected annealing time (168 hours), which is specified in the formula of the invention, is optimal from the point of view of expediency.

The invention can be used in the production of a patent-protected thermoelectric material (41), capable of forming increased thermo-EMF values.

Sources of information 65 1. Kierr K.O., Eshepregdeg p. OageseiNishpo pa Kgizia|yvigKkISHg mop TITIZ., TIdZpZ; pa TITIZe // 7.

Myshgpogzgsp. - 1984. - va.zor. - 5.705-712.

2. Karge 5., byShaga M., Rpapashi 5. Zyg Ie diddgatte de rpasez di zuziet I(Naiyint - zotsite // S.K. Asavy.

All together. Ragiv - 1974. - T.S278, M16. - R.1043-1046. 3. Barchiy I.E., Lazarev V.B., Peresh E.Yu. Phase equilibria in the TI25(5e)-Tizo(5e")/HNH systems. - 1987. dog T.82, Mo7. - with. 1786-1788. - a prototype. 4. Betsa V.V. Thermoelectric element. Patent of Ukraine Mo431814A. - 2001.

Claims (1)

The formula of the invention , , , , y y , The method of obtaining thallium (I) - titanium (IM) tetrasulfide (TI Ti5)), which includes stepwise heating of quartz ampoules vacuumed to 0.13 Pa, containing the initial components in the required stoichiometric ratio, to maximum temperature and exposure at the same temperature for 24 hours and subsequent annealing at 650OK, which differs in that elemental thallium, titanium and sulfur are used as initial components for synthesis, the maximum synthesis temperature is 1073-5K, and annealing lasts 16841 hours. c o IS) c "- "c) m. shi s ;" -I ("c) - o 50 sl F) ime) 60 b5