HYDROTHERMAL SYNTHESIS OF COPPER SELENIDES CSCU4SE3 AND CSCUSE4

Synthetic investigations of the Cs-Cu-Se system were carried out in ev acuated sealed fused silica ampoules at temperatures below 200-degrees -C. Reactions between CsCl, A2Sex (A = Na, K; x = 2, 4,5) and Cu under hydrothermal conditions were examined. Two phases have been isolated: a layered CsCu4Se3 phase (P4/mmm, Z = 1, a = 4.090 (2) angstrom, c = 10.089 (2) angstrom, R = 3.83, R(w) = 4.39%) and a linear chain CsCuSe 4 phase (P2(1)2(1)2(1), Z = 4, a 5.574 (2) angstrom, b = 9.020 (2) ang strom, c = 13.931 (3) angstrom, R = 2.44, R(w) = 3.21%). The structure s have isostructural parents KCu4S3 and (NH4)CuS4, respectively. This report illustrates, for the first time, the propensity of polychalcoge nide salts to act as reagents in hydrothermal copper chemistry. (C) 19 94 Academic Press, Inc.