Peculiarities of the synthesis and polymorphic transformations and the crystalline structure of M-modifications of LnTaO_4

摘要

The succession of the processes of chemical synthesis of LnTaO_4 (Ln = Nd, Sm, Eu, Gd, Ho, Er, Lu) is determined. Peculiarities of the mutual transformations of their polymorphic modifications (M- and M~Ifergusonite structure types) have been studied, and the regions of their thermodynamic stability have been outlined. Details of the crystal structures of the M-modification of LnTaO_4 (Ln = Sm, Eu, Gd, Er, Lu) have been determined for the first time by X-ray powder diffraction.