Refined structural studies on the fluorite-related polymorphs of sol-gel undoped and Eu-doped yttrium tantalates.

Compounds with the general formula REMO (RE = rare earth ions; M = Ta, Nb, Sb, Ru, Ir, Os, Re, .), crystallize as a fluorite-related structure, forming polymorphs with different space groups. The space group strongly depends on the RE and M ionic radii and processing conditions.