BA Binary alloys CO CRYSTAL-STRUCTURE Dielectric losses Double perovskites Energy gap Grainsize IMPEDANCE Monoclinic symmetry NI OXIDE Optical and dielectric properties Permittivity Perovskite Perovskite compounds RELAXATION Rietveld refinement SR Scanning electron microscopy Solid state method Space Groups Synthesised Tellurium compounds UV-Vis diffuse reflectance spectroscopy X-ray diffraction data ZN