AC susceptibility Binary alloys Dielectric losses Double perovskites Energy gap Grainsize Monoclinic symmetry Optical and dielectric properties Permittivity Perovskite Perovskite compounds Perovskite manganites Rietveld refinement Scanning electron microscopy Solid state method Space Groups Synthesised Tellurium compounds UV-Vis diffuse reflectance spectroscopy X-ray diffraction data X-ray powder diffraction