Synthesis and structure investigation of ternary oxides based on molybdenum and lanthanum

•Samples of lanthanum–molybdenum pyrochlores MgLa2MoO7 and CaLa2MoO7 are synthesized.•The X-ray diffraction study, SEM, IR and DTA investigations were carried out.•Structural parameters of the samples at room and high temperature were determined.

Compounds of the ternary oxides class with formulae MgLa2MoO7 and CaLa2MoO7 were synthesized by the citrate method. According to the SEM and X-ray analysis data the samples are referred to pyrochlore with a tetragonal (MgLa2MoO7) and monoclinic (CaLa2MoO7) crystal lattice. At the temperature of 900 °C the compound CaLa2MoO7 is subjected to phase transition from the monoclinic crystal system to the cubic one. According to the differential thermal analysis data, this transition occurs through the intermediate states characterized by non-monotonic changes of lattice parameters of the unit cell. In general, the compounds are characterized by minor structural distortions compared with the cubic structure of pyrochlore.