Characterization of structure, chemical bond and microwave dielectric properties in Ca0.61Nd0.26TiO3 ceramic substituted by chromium for titanium

Abstract We studied the phase constitutions, microstructure, chemical bond and microwave dielectric properties for Ca0.61Nd0.26Ti1-xCrxO3 (0 ≤ x ≤ 0.03) ceramics synthesized by solid-state reaction using SEM, X-ray diffractometer, Raman spectroscopy, microwave measuring system, etc. Although the second phase TiO2 appeared when x ≥ 0.015 as presented in XRD patterns, TiO2 was confirmed to have no effects on the tendency of microwave dielectric properties as a function of x value. The SEM images showed that the grain size decreased as Cr content increased, which could be explained by that doping Cr increased the grain boundary energy or decreased surface energy for Ca0.61Nd0.26TiO3 ceramic. The SRO effects enhanced with increase of Cr substitution, which was verified by Raman spectra. The dielectric constant and τf value were concerned with the average ionicity of chemical bond and the ionic polarizability for Ca0.61Nd0.26Ti1-xCrxO3 ceramics. The SEM images suggested that the optimized sintering temperatures was 1400 °C for samples with x = 0.01. The XPS spectra and the trend of Q × f value indicated that the balanced amount of Cr substitution could restrain the generation of Ti3+. Hence, the Q × f value of Ca0.61Nd0.26Ti1-xCrxO3 ceramics reached the maximum of 16,078 GHz at x = 0.01 compared with that of 11,425 GHz in pure Ca0.61Nd0.26TiO3 ceramic.