COMPOUND FORMATION AND LOCAL-STRUCTURE IN TERNARY METAL-PHOSPHORUS-SELENIUM SYSTEMS

The formation of ternary compounds is investigated in a variety of M-P-Se systems (M = Cd, Sn, Zn, Ca, Cu, In), using X-ray powder diffraction and P-31, Se-77, Cd-113, Sn-119 MAS NMR. Compound formation in these systems is dominated by the P-Se anions, [P2Se6]4- and [PSe4]3-. These two types of local structures can be identified on the basis of P-31 chemical shift ranges and distinguished with the help of the Dipolar Recovery at the Magic Angle (DRAMA) technique. A new compound was found and characterized as Ca2P2Se6, orthorhombic, a = 5.73(l) angstrom, b = 9. 86(1) angstrom, c = 15.78(l) angstrom, with [P2Se6]4- units. (C) 1994 Academic Press, Inc.