RU2434809C1 - Method of producing powdered trisulphides of europium, lanthanide and copper - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to inorganic chemistry and specifically to a method of producing complex sulphides of rare-earth elements used as semiconductor materials. The method of producing powdered trisulphides of europium (II), lanthanide (III) and copper EuLnCuS₃ (Ln=La-Lu) involves exposing an initial charge of an argon stream to sulphiding gases (H₂S, CS₂), obtained from decomposition of ammonium rhodanide. The initial charge used is a mixture of simple and complex oxides obtained via thermal decomposition at 1000 K together with crystalline nitrates of copper, europium and lanthanide. Sulphidation takes place in a stream of H₂S and CS₂ (4-6 eq/l) at 970 K for 15 hours, at 1120 K for 7 hours and at 1220 K for 3 hours.

EFFECT: invention enables to shorten duration and lower temperature of synthesis, increase phase homogeneity during synthesis of trisulphides EuLnCuS₃ (Ln=La-Lu) and obtain substances in an active state for pressing.

2 cl, 3 ex

Description

The invention relates to the field of inorganic chemistry, and in particular to a method for producing complex sulfides of rare-earth elements used as semiconductor materials.

A known method of producing copper trisulfides EuLnCuS ₃ (Ln = Gd-Lu) no solid-phase reaction using rare earth sesquioxides (Ln ₃ O ₃ ) and copper oxide CuO as starting materials [1]. Stoichiometric mixtures of starting materials were heated in a graphite boat at 1170–1320 K for 18–36 h in a stream of a mixture of CS ₂ and N ₂ gases, obtained by bubbling N ₂ through a CS ₂ liquid at room temperature. The synthesis included several stages of grinding the resulting product.

The disadvantage of this method is that, as the authors note, this method failed to obtain the EuNdCuS ₃ phase, and the samples where Ln = Sm, Ho, and Er contain (Eu, R) ₂ O ₂ S (not more than 3%) )

The authors of [2] tested the ceramic method, which consists in thoroughly mixing accurate weighed portions of commodity oxides with subsequent sulfidation. This traditional method for obtaining many types of structural and functional ceramics has a number of significant drawbacks, the main of which is the duration of the heat treatment due to the rather large grain size and heterogeneous mixing of the reagents, which can lead to irreproducibility of electrophysical properties. Processed substances may become contaminated with decaying quartz. The degree of contact of the phases in the state of the bulk volume is relatively small. To achieve uniformity in the distribution of cations in a substance due to their mutual diffusion, a long heat treatment time of up to 150 hours is required.

The following method is known for producing complex sulfide samples: the ampoule method in evacuated and sealed quartz ampoules from Cu and S elements gives Cu ₂ S. SrS and Ln ₂ S ₃ sulfides are synthesized from SrSO ₄ and Ln ₃ O ₃ in an H ₂ S and CS ₂ stream at 1300 K. The charge of the initial sulfides in the ratio 2SrS: 1Cu ₂ S: 1Ln ₂ S _{3 was} fused in a graphite crucible in a sealed quartz ampoule. The ampoule was processed by induction in a high-frequency current generator. The substance was transferred to the melt three times, then it was slowly cooled to a temperature 30-70 K below the melting point. Cooling was performed in the off-furnace mode. Ampoules were annealed at 1050 K for 480 h [3].

The disadvantage of this method is that long-term annealing is required to obtain a homogeneous sample, which ensures the chemical interaction of the unreacted phases with the formation of a complex sulfide, due to incongruent melting, complex sulfides A ^II LnCuS ₃ (A = Sr) are not obtained in a homogeneous state when they are cooled from melt. SrS crystals and a eutectic between the SrLnCuS ₃ and CuLnS ₂ phases are present on the microstructure of samples of samples cooled from the melt. The authors note that not all annealed samples were completely homogeneous, with MSA, trace amounts of impurity phases (CuLnS ₂ and SrS) are detected.

The purpose of the invention is to reduce the duration and temperature of synthesis, increase phase uniformity in the synthesis of trisulfides EuLnCuS ₃ (Ln = La-Lu), obtain substances in an active state for pressing.

The goal is achieved by first obtaining a precursor - a chemical compound in which the atoms of the main components are located in the necessary proximity to each other. This allows one to remove diffusion difficulties and transfer the reaction to the kinetic region, which is associated with a noticeable acceleration of synthesis. A mixture of simple and complex oxides obtained by thermal decomposition at 1000 K of co-crystallized copper, europium and lanthanide nitrates is used as a precursor, and sulfidation is carried out in a stream of H ₂ S and CS ₂ (4-6 equiv / l) at 970 K for 15 hours, at 1120 K for 7 hours, at 1220 K for 3 hours.

The inventive method is as follows.

Example 1. Weighed copper "os.ch. 11-4 ", lanthanum oxide" LaO-D ", europium oxide" EvO-Zh "is calculated based on the gross chemical composition of the EuLaCuS ₃ sample and its mass. The surface of the copper plate is previously mechanically cleaned of the layer of basic carbonates with which it is coated in air. REE oxides are calcined at 1050 K to constant weight in order to remove absorbed moisture and CO ₂ . To obtain 20 g of EuLaCuS ₃ sulfide, 2.8143 g of copper, 7.2333 g of lanthanum (III) oxide, 7.4578 g of europium (II) oxide are mixed at room temperature. The resulting mixture of powders at room temperature is placed in a heat-resistant flat-bottomed flask and dissolved in 50 ml of concentrated nitric acid brand "hch". The resulting solution containing cations Cu ²⁺ Eu ²⁺ , La ³⁺ , is slowly (4-5 hours) evaporated to a dry residue, preventing boiling and spraying of the solution. The dry residue is thoroughly mixed and placed in a quartz glass, which, in turn, is lowered into an open quartz reactor, which is a tube with a diameter of 40 mm and a height of 500 mm. The reactor with the charge is placed in an electric heating furnace located in a fume hood, and maintained at a temperature of 1000 K for 2 hours. In this case, the process of destruction of lanthanum nitrate begins to occur at 310-320 K. Copper salt decomposes with melting of about 373-473 K. During the heat treatment, the formed CuO and EuO oxides entered into chemical interaction with each other with the formation of CuEu ₂ O ₄ by the solid-state reaction: CuO + Eu ₃ O ₃ → CuEu ₂ O ₄ . According to XRD data, oxide sinter (ash-black) obtained after the decomposition of nitrates has a phase composition: CuEu ₂ O ₄ , La ₂ CuO ₄ , La ₂ O ₃ . Oxide particles up to 40 μm in size have distinct faces, and the obtained distribution spectrum of elements, on which there are no characteristic lines of nitrogen, indicates complete decomposition of nitrates. The oxide cake is thoroughly mixed and placed in the space between the quartz glass (23 mm in diameter) and the gas supply quartz tube (9 mm in diameter) and all this is placed in a quartz pipe (30 mm in diameter and 500 mm high), which has a sealed bottom and a gas outlet for removal of gaseous reaction products from the reactor zone. An external quartz tube protects the synthesized substance from oxidation. An argon stream with sulphiding gases (H ₂ S and CS ₂ 4-6 eq / L) obtained by decomposition of ammonium thiocyanate is passed through the charge. After synthesis, the resulting product is cooled in a reactor in a stream of argon with sulfidizing gases. The mixture is ground and examined by methods of physico-chemical analysis. The reaction is carried out until the reflections of the phases of the initial charge or intermediate products disappear on the X-ray diffraction patterns. A kinetic curve is constructed for each temperature — the yield of the product as a function of time. It was experimentally established that a homogeneous sulfide powder is guaranteed to be obtained with EuLaCuS ₃ at 970 K for 15 hours, at 1120 K for 7 hours, at 1220 K for 3 hours.

Example 2. Preparation of the starting components and preparation of a mixture of nitrates is carried out analogously to example 1. A mixture of nitrates is placed in a spray bottle and sprayed into the prepared solution by injection into a quartz reactor, previously placed in a furnace heated to 1000 K. The resulting powdery mixture of oxides is collected from the walls of the reactor, ground and then carry out sulfidation analogously to example 1 at 1220 K for 2-3 hours.

Example 3. To obtain 20 g of EuGdCuS ₃ sulfide at room temperature, 2.7041 g of copper, 7.7329 g of gadolinium (III) oxide, 7.1659 g of europium (II) oxide are mixed. The experiment is carried out analogously to example 2 at 1220 K for 3 hours.

Literature

1. Wakeshima M., Furuuchi F., Hinatsu Y. Crystal structures and magnetic properties of novel rare-earth copper sulfides, EuRCuS ₃ (R = Y, Gd-Lu) // Journal of Phusics: Condensed Matter 16 (2004) 5503 -5518.

2. Bamburov V.G., Andreev O.V. Simple and complex sulfides of alkaline earth and rare earth elements // Journal of Inorgan. Chemistry, 2002, v. 47, No. 4, p. 676-683.

3. Sikerina N.V., Andreev O.V. The crystal structure of SrLnCuS ₃ compounds (Ln = Gd, Lu) // Journal of Inorganic Chemistry, 2007.- V. 52. - No. 4 - p. 641-644.

Claims (2)

1. A method of producing powders of europium (II) trisulfides, lanthanides (III) and copper EuLnCuS ₃ (Ln = La-Lu), consisting of exposing the initial charge to an argon stream with sulfidizing gases (H ₂ S, CS ₂ ) obtained by decomposition of thiocyanate ammonium, characterized in that to reduce the synthesis time, to obtain homogeneous complex sulfides in an active state for pressing, a mixture of simple and complex oxides obtained by thermal decomposition at 1000 K of co-crystallized copper, europium and lanthanide nitrates is used as the initial charge, and sul fidirovanie carried out in a stream of H ₂ S and CS ₂ (6.4 eq / l) at 970 K for 15 hours, at 1120 K for 7 hours at 1220 K for 3 hours. 2. The method according to claim 1, characterized in that the mixture of complex oxides is obtained by spraying nitrate solutions when they are injected into a quartz reactor previously placed in an oven heated to 1000 K, and the resulting mixture of oxides is subjected to sulfidation at 1220 K for 2-3 hours