La8+xTi8+yS24O4 Compounds Where x + y ≤ 2: A Series of Phases with Mixed-Valent Titanium

Three new titanium oxysulfides, La8.75Ti9.25S24O4, La8.50Ti9.50S24O4, and La8.10Ti8.05S24O4, were prepared by high-temperature methods (1025−1050 °C; ∼80−150 h) from La2S3, Ti, S, and either La2O3 or TiO2 as oxygen sources. LaCl3 (∼10−30 wt %) was added as a flux. The compounds were characterized by single-crystal X-ray diffraction, neutron activation analysis, and EDX analysis. All three compounds contain common [(Ti4S2O4)(TiS6)4/2](12+δ)- oxysulfide layers and disordered/variable composition titanium sulfide layers that alternately stack along the c-axis of the unit cell. The titanium sulfide layers contain extensive La/Ti solid solution formation and are characterized by 5-fold disorders at the M(2) octahedral sites and 2-fold disorders at the M(3) sites. These compounds are members of a series of compounds with the general formula La8+xTi8+yS24O4, where (x + y) ≤ 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 = 10.4...