Synthesis and crystal structure of the lanthanum titanate tellurate LaTi(Ti0.25Te0.75)O6 and its relationship to PbSb2O6 and Sr(MnTe)O6

Single crystals of LaTi(Ti0.25Te0.75)O-6 have been prepared by solid state reactions. X-ray investigations led to trigonal symmetry, space group C-3(1)-P3, a = 5.141(10), c = 5.218(10) Angstrom, Z = 1. The compound is characterized by a predominantly ordered distribution of Ti4+ and Te6+. Typical features of the crystal structure are staggered layers containing edge connected TiO6 and (Ti,Te)O-6 octahedra. The layers are connected by La3+ ions receiving an octahedral coordination by the surrounding oxygen ions. The relationships to the PbSb2O6 type and the recently described compound Sr(MnTe)O-6 are discussed.