First principles approach and experimental exploration of a new double perovskite phase Sr2(In0.33 Sn0.33Sb0.33)2O6: evaluation of structural, optical, and dielectric properties

A new double perovskite phase, Sr2(Sn0.33Sb0.33In0.33)2O6, was successfully synthesized via a solid-state reaction and comprehensively characterized using both experimental and theoretical techniques. Powder X-ray diffraction was used to determine the crystal structure, while scanning electron microscopy (SEM) revealed a high degree of densification and uniform grain distribution across the ceramic. Raman and Fourier-transform infrared (FTIR) absorption spectra of the powder present broad bands predominantly due to different stretching modes of the various SnO32−, InO32− and SbO32− octahedra in the region ν = 400–800 cm−1. An analysis of the UV-Vis diffuse reflectance spectrum shows excellent optical transparency and gives an estimation of an optical gap Eg ∼ 3.6 eV on bulk Sr2(Sn0.33Sb0.33In0.33)2O6, making this material a promising candidate for optoelectronic devices. Density Functional Theory calculations further validated the experimental findings, confirming the crystal structure and providing insight into the electronic and vibrational properties. Impedance spectroscopy revealed non-Debye dielectric relaxation and confirmed typical negative temperature coefficient of resistance (NTCR) behavior, underscoring the material's potential for temperature-sensing applications. The primary conduction mechanism, modeled as correlated barrier-hopping (CBH), was complemented by an Arrhenius-type process with activation energies of 0.33 eV and 0.9 eV across two distinct temperature ranges.