The anion and cation deficient phase Bi0.95 In0.05 O1.5 (Bi1.9 In0.1 O3) was synthesized and experimentally investigated using X-ray diffraction and vibrational spectroscopy (Infrared and Raman). The non-stoichiometric phases are similar to sillenite family type γBi2O3 and crystallize in the I23 space group. The crystal structure was determined by full profile Rietveld analysis of the powder diffractogram. It is formed by a sequence of BiO5E polyhedra (E lone pair of bismuth) and MO4 polyhedra (M = In, Mg). The set of MO4 polyhedra are localized in cavities generated by BiO5E polyhedra. The vibrational spectroscopic study revealed the existence of three regions; low, intermediate and high-frequency region. They are attributed to Bi-O stretching mode, In / Mg-O vibrations and cationic displacements respectively.

Defect pyrochlore oxide powders ABi 2 Ta 5 O 16 , in the pseudo-binary systems BiTaO 4 –ATa 3 O 8 (A = Na, Tl), were prepared by solid state method. The structural study showed that all oxides crystallize in a cubic system with the space group Fd 3 m , the lattice parameter “a” were determined using Rietveld refinement method. For systematic study on densification from powders, the samples were pressed with a uniaxial pressure into pellets; sintering temperature, holding time and heating rate were optimized. Techniques, including X-ray diffraction, IR-Raman, MEB, dilatometry, were employed to investigate the structure and the morphology of the synthesized powders and sintered materials. The dielectric characteristics, relative permittivity and dielectric losses (tgδ), determined at room temperature are comparable to those of other pyrochlores.

In the original published version of this article, Table 1 was incorrectly referenced in section 3.2.6 -Influence of the holding time. The table should only have been referenced in section 3.1.1 -XRD diffraction and the table should have been at this position in the manuscript. This error was introduced during the typesetting of the article, the publisher apologises for this error. Both the HTML and PDF versions of the article have been updated to correct the error.