MULTI-ELEMENT METAL CHALCOGENIDE

Abstract: A novel, multi-element metal chalcogenide is disclosed which has the following general formula (I): X (1-a)x X′ ax Y y Z z (I) wherein X stands for at least one element selected from Bi, Sb and As, X° stands for at least one element selected from Pb, Sn and Ge, Y stands for at least one element selected from Ti, V, Nb and Ta, Z stands for at least one element selected from S, Se and Te, a is a number of 0-1, x is a number of 0.8-1.2, y is a number of 0.8-1.2 or 1.6-2.4 and z is a number of 2.4-3.6 when y is 0.8-1.2 or a numeral of 4.0-6.0 when y is 1.6-2.4.

Description: This invention relates to a multi-element metal chalcogenide useful for application to batteries, optical elements and superconducting materials. A chalcogen is a general term for an element of the group consisting of sulfur (S), selenium (Se) and tellurium (Te). Since chalcogens are small in electronegativity as compared with oxygen, metal chalcogenides have less ionic bonding property but greater covalent bonding property as compared with metal oxides. Accordingly, metal chalcogenides are essentially great in anisotropy of bonding and tend to form a linear or planar substance having a layered, chain or channel structure. In respect of physical properties, the highest occupied level of the electrons of chalcogens is lower than that of oxygen. Thus, while oxides chiefly form insulators and semiconductors with a large band-gap, chalcogenides tend to form good electrical conductors and semiconductors with a small band gap. Taking advantage of these structural and physical characteristics, metal chalcogenides are applicable widely to optical materials, such as solar batteries, non-linear optical materials and luminescent materials, superconducting materials (especially in the case of Chevrel compounds), and materials for lithium batteries, etc. At present known chalcogenides include chalcogen spinel (such as CdCr₂S₄), chalcopyrite (such as CuInS₂) and Chevrel (such as PbMo₆S₈). Gmelin Handbuch der Anorganischen Chemie, 8th Edition, part B4, 1973, Verlag Chemie, page 299 discloses the chalcogenide PbNbS₃. Yet further chalcogenides are disclosed in FR-A-1597115; and Gmelin Handbuch der Anorganischen Chemie, 9th Edition, part A3, 1981, Verlag Chemie, pages 251-255 and 268-273. In accordance with the present invention there is provided a chalcogenide having the following general formula (I): X (1-a)x X' ax Y y Z z (I) wherein X stands for at least one element selected from Bi, Sb and As, X' stands for at least one element selected from Pb, Sn and Ge, Y stands for at least one element selected from Ti, v, Nb and Ta, Z stands for at least one element selected from S, Se and Te, a is 0-1, x is 0.8-1.2, y is 1.6-2.4 and z is 4.0-6.0. More specifically, the chalcogenides according to the present invention include the following three kinds: (1) Chalcogenides having the following composition: X x Y y Z z wherein: X : Bi, Sb and/or As, Y : Ti, V, Nb and/or Ta, Z : S, Se and/or Te, x : a number of 0.8 ≦ x ≦ 1.2, y : a number of 1.6 ≦ y ≦ 2.4, and z : a number of 4.0 ≦ z ≦ 6.0; (2) Chalcogenides having the following composition: X' x Y y Z z wherein X': Pb, Sn and/or Ge, Y : Ti, V, Nb and/or Ta, Z : S, Se and/or Te, x : a number of 0.8 ≦ x ≦ 1.2, y : a number of 1.6 ≦ y ≦ 2.4, and z : a number of 4.0 ≦ z ≦ 6.0; (3) Chalcogenides having the following composition: X (1-a)x X' ax Y y Z z wherein X : Bi, Sb and/or As, X': Pb, Sn and/or Ge, Y : Ti, V, Nb and/or Ta, Z : S, Se and/or Te, a : a number of 0 < a < 1, x : a number of 0.8 ≦ x ≦ 1.2, y : a number of 1.6 ≦ y ≦ 2.4, and z : a number of 4.0 ≦ z ≦ 6.0. The multi-element metal chalcogenide according to the present invention may be prepared by a method including the steps of mixing powdery elements and/or powdery metal chalcogenides (MZ n where M is a metal, Z is S, Se or Te and n is a number of 1 ≦ n ≦ 2) in amounts providing a composition corresponding to that of the above general formula, charging the mixture in a closed vessel such as a quartz tube maintained under vacuum or in an inert atmosphere, and heating the mixture at 400-1200 °C. The resulting product is cooled to room temperature to obtain a multi-element metal chalcogenide. The thus obtained multi-element metal chalcogenide is generally in the form of brown to black powder and its powder X-ray diffraction pattern shows diffraction lines attributable to a set of parallel planes. Depending on conditions, the product is obtained in the form of laminar crystals which easily undergo cleavage. This suggests that the product has a layered structure. In the metal chalcogenides according to the present invention, the composition of the elements X (or X + X'), Y and Z can be designated as 1:2:5 (XY₂Z₅). Since, however, the element Z may be non-stoichiometric, the number z for the element Z is not always exactly 3 or 5 but ranges from 4.0 to 6.0. This also applies to the numbers x and y. The following examples will further illustrate the present invention. Example 1 A multi-element metal chalcogenide having the composition of the above group (1) was prepared as follows: Powdery elements corresponding to the composition shown in Table 1 were weighed in a proportion corresponding to the composition, enclosed in a quartz vessel under vacuum, heated at a temperature of 400-1200 °C and then cooled to room temperature. The composition of the metal chalcogenides thus obtained and the interplanar spacings (Å) of the main diffraction lines in the powder X-ray diffraction pattern of the chalcogenides are shown in Table 1. Sample No. Composition Interplanar Spacing of Main Diffraction Lines (Å) X x Y y Z z 13 Bi Ti₂ S₅ 17.0 8.51 5.65 4.23 3.39 2.83 14 Bi V₂ S₅ - - 5.65 4.23 3.39 2.82 15 Bi Nb₂ S₅ - - 5.76 4.36 3.47 2.90 16 Bi Ta₂ S₅ - 8.76 5.83 4.38 3.51 - 17 Bi Nb₂ Se₅ - - 6.16 4.58 3.68 3.06 18 Bi TiV S₅ - - 5.65 4.23 3.39 2.82 19 Bi VNb S₅ - - 5.71 4.30 3.43 2.86 20 Bi NbTa S₅ - - 5.80 4.37 3.49 - 21 Sb Ta₂ S₅ - 8.75 5.82 4.37 3.50 - 22 Bi 0.5 Sb 0.5 Ta₂ S₃ - 8.76 5.83 4.38 3.51 - Example 2 Multi-element metal chalcogenides having the compositions of the group (2) were prepared in the same manner as that in Example 1. The composition of the metal chalcogenides thus obtained and the interplanar spacings (Å) of the main diffraction lines in the powder X-ray diffraction pattern of the chalcogenides are shown in Table 2. Sample No. Composition Interplanar Spacing of Main Diffraction Lines (Å) X x Y y Z z 30 Pb Ta₂ S₅ - - 6.03 4.51 3.62 2.57 31 Sn Nb₂ S₅ - - 5.95 4.44 3.55 - 32 Sn Ta₂ S₅ - 8.94 5.91 4.46 3.58 2.56 33 Pb Nb₂ Se₅ - - 6.24 4.67 3.74 3.12 34 Pb Ta₂ Se₅ - - 6.29 4.72 3.77 3.13 35 Sn Nb₂ Se₅ - - 6.20 4.63 3.71 3.09 36 Sn Ta₂ Se₅ - 9.42 6.29 4.70 3.76 3.12 37 Pb 0.5 Sn 0.5 Ta₂ S₅ - - 5.97 4.49 3.60 2.57 38 Pb NbTa S₅ - - 6.01 4.50 3.61 - 39 Sn NbTa S₅ - - 5.93 4.45 3.57 - Example 3 Multi-element metal chalcogenides having the compositions of the group (3) were prepared in the same manner as that in Example 1. The composition of the metal chalcogenides thus obtained and the interplanar spacings (Å) of the main diffraction lines in the powder X-ray diffraction pattern of the chalcogenides are shown in Table 3. Sample No. Composition Interplanar Spacing of Main Diffraction Lines (Å) X (1-a)x X' ax Y y Z z 52 Bi 0.5 Pb 0.5 Nb₂ S₅ - 5.88 4.43 3.53 2.95 53 Bi 0.5 Sn 0.5 Nb₂ S₅ - 5.85 4.40 3.51 - 54 Bi 0.5 Pb 0.5 Ta₂ S₅ - 5.93 4.45 3.57 - 55 Bi 0.5 Sn 0.5 Ta₂ S₅ - 5.87 4.42 3.55 - 56 Bi 0.5 Pb 0.5 Nb₂ Se₅ - 6.20 4.63 3.71 - 57 Bi 0.5 Sn 0.5 Nb₂ Se₅ - 6.18 4.61 3.70 -

Claims: A chalcogenide having the following general formula (I): X (1-a)x X' ax Y y Z z (I) wherein X stands for at least one element selected from Bi, Sb and As, X' stands for at least one element selected from Pb, Sn and Ge, Y stands for at least one element selected from Ti, V, Nb and Ta, Z stands for at least one element selected from S, Se and Te, a is 0-1, x is 0.8-1.2, y is 1.6-2.4 and z is 4.0-6.0. A chalcogenide according to Claim 1, having the following general formula: X x Y y Z z wherein X, Y and Z and the numbers x, y and z are as defined in Claim 1. A chalcogenide according to Claim 1, having the following general formula: X' x Y y Z z wherein X', Y and Z and the numbers x, y and z are as defined in Claim 1. A chalcogenide according to Claim 1, having the general formula: X (1-a)x X' ax Y y Z z wherein X, X', Y and Z and the numbers x, y and z are as defined in Claim 1, and a is a number of 0 < a < 1.

Inventors: GOTOH, YOSHITO, OHSAWA, YOSHINAO
Applicants: DIRECTOR-GENERAL OF THE AGENCY OF INDUSTRIAL SCIENCE AND TECHNOLOGY
Application year: 1989
Main classification: C01B19
IPC codes: C01B19, C01G1, C01B17