Polymorphism of LaTaTiO6.

Two polymorphs of LaTaTiO6, i.e. monoclinic and orthorhombic, were synthesized by solid-state reaction technique. Both were found to be isostructural with analogous niobium compounds which were used as structural models. Structural characterization was performed on X-ray powder data by Rietveld refinement procedure which resulted in final Rwp values of 7.01 and 7.52% for orthorhombic and monoclinic form, respectively. Comparisons between both title compounds are given and their plausibility is proved by bond valence sums and global instability index calculations. For the monoclinic polymorph, dielectric properties measured at 1 MHz are also given.