LA8-LESS-THAN-OR-EQUAL-TO-2 - A SERIES OF PHASES WITH MIXED-VALENT TITANIUM(XTI8+YS24O4 COMPOUNDS WHERE X+Y)

Three new titanium oxysulfides, La8.75Ti9.25S24O4, La8.50Ti9.50S24O6, and La8.10Ti8.05S24O4, were prepared by high-temperature methods (1025 -1050 degrees C; similar to 80-150 h) from La2S3, Ti, S, and either La 2O3 or TiO2 as oxygen sources. LaCl3 (similar to 10-30 wt %) was added as a flux. The compounds were characterized by single-crystal X-ray d iffraction, neutron activation analysis, and EDX analysis. All three c ompounds contain common (2)(infinity)[(Ti4S2O4)(Ti-S-6)(4/2)]((12+delt a)-) oxysulfide layers and disordered/variable composition titanium su lfide layers that alternately stack along the c-axis of the unit cell. The titanium sulfide layers contain extensive La/Ti solid solution fo rmation and are characterized by 5-fold disorders at the M(2) octahedr al sites and 8-fold disorders at the M(3) sites. These compounds are m embers of a series of compounds with the general formula La8+xTi8+yS24 O4, where (x + y) less than or equal to 2 and the oxidation states of Ti can vary from +3 to +4. Crystal data (153 K) of La8.75Ti9.25S24O4: tetragonal space group P4/mmm, a = 10.4205(8) Angstrom, c = 8.3848(6) Angstrom, V = 910.5(1) Angstrom(3), Z = 1, R(F) = 3.88% and wR(F-2) = 7.22%. For La8.50Ti9.50S24O4, tetragonal space group P4/mmm, a = 10.41 01(3) Angstrom, c = 8.396(1) Angstrom, V = 909.9(1) Angstrom(3), Z = 1 , R(F) = 3.54% and wR(F-2) = 8.16%. For La8.10Ti8.05S24O4, tetragonal space group P4/mmm, a = 10.4212(3) Angstrom, c = 8.233(2) Angstrom, V = 894.1(2) Angstrom(3), Z = 1, R(F) = 4.25% and wR(F-2) = 11.12%.