Sodium holmium double silicates with the apatite structure and compositions NaHo 9 (SiO 4 ) 6 O 2 and Na 2 Ho 8 (SiO 4 ) 6 O have been prepared by a sol-gel process and characterized by X-ray diffraction. The crystal structure of NaHo 9 (SiO 4 ) 6 O 2 has been refined, and the electrical conductivity of both compounds has been measured.

Двойные силикаты натрия и гольмия со структурой апатита состава Na2Ho8(SiO4)6O и NaHo9(SiO4)6O2 синтезированы золь–гель-методом. Соединения изучены методом рентгенофазового анализа, уточнена кристаллическая структура NaHo9(SiO4)6O2, измерены электрофизические свойства.

Samarium substitution for neodymium in the Nd 5 Mo 3 O 16 compound has been studied by X-ray diffraction, scanning electron microscopy, and IR spectroscopy. The results demonstrate that fluorite-like Nd 5– x Sm x Mo 3 O 16 solid solutions exist in the range x ≤ 2. The electrical conductivity of the solid solutions increases with increasing samarium content in the range x = 0–1. Structure refinement by the Rietveld method for Nd 4 SmMo 3 O 16 has shown that the Nd(2) coordination polyhedron in this solid solution is distorted more severely than that in the structure of Nd 5 Mo 3 O 16 .

The substitution neodymium for ytterbium in compounds Nd 5 Mo 3 O 16 was investigated by X-ray diffraction. Solid solution Nd 5-x Yb x M o3 O 16 with cubic fluorite-related structure is formed in the composition rage up to x = 0,7. The substitution limit was determined by inflection of parameter a of cubic phase and by disappearing-phase method. It is near 3 at. %. The dependence of specific conductivity on composition is non-linear and has the minimum on x = 0,05.