Development and characterization of Ca9-xSrxNd2W4O24 (x = 0, 1, 2, 3, 4, 5, 6, 8, 9) functional ceramics

Abstract

Solid solutions of Ca_9-xSr_xNd₂W₄O₂₄ (x = 0, 1, 2, 3, 4, 5, 6, 8, 9) functional ceramics are prepared through the conventional solid state ceramic route. The XRD analysis revealed the tetragonal structure of the compounds and is confirmed using Raman and Fourier Transform Infrared Spectroscopy. The lattice parameters of Ca₉Nd₂W₄O₂₄ and Sr₉Nd₂W₄O₂₄ are calculated using XRD patterns and the vibrational bands are assigned using vibrational spectroscopic analysis. The absorption edges of the reflectance spectra for all the samples lie between the wavelength range 330–360 nm (UV region) point out the practical use of these ceramics as UV filters. The band gap energy is calculated using Tauc plot relation and the elemental compositions of the ceramics are examined through the energy dispersive X-ray spectroscopy (EDS). From the FESEM images, it is evident that all the samples attain maximum densification with minimum porosity. The average grain size of the samples is calculated and these results substantiate that Sr₉Nd₂W₄O₂₄ contains a greater number of large sized grains (with fewer boundaries) than the other samples. The dielectric constant of the samples determined at 25 °C and 850 °C showed that the solid solutions possess high dielectric constant at 5 MHz for both temperatures, compared to pure samples. The impedance spectroscopic studies are employed to investigate the grain, grain boundary and electrode contribution in the electrical properties of the sintered samples. The ionic conductivity of the pellets at different temperatures is estimated using Arrhenius relation, for which the resistance is obtained from the semicircle in the Cole-Cole plot.