Band gap engineering and microwave dielectric properties evolution of mixed (Sr, La, Ce) TiMgO3 titanate–aluminate system

Abstract

A mixed perovskite titanate-aluminate [(1-x)(Sr0.6La0.2Ce0.2Ti0.8Mg0.2O3)-xNdAlO3 for x = 0.1 to 0.4] solid solution was successfully synthesized. X-ray diffraction patterns (XRD) and Rietveld refinement results indicated a stable perovskite phase with a cubic structure, in which Nd3+ occupies the A-site randomly while Al3+ occupies the B-site. No additional reflection spots (superlattice reflections) were detected in the HRTEM pattern (see SAED), confirming the cubic symmetry. All samples showed small Urbach tails, mainly due to compositional disorder. Microstructural analysis based on atomic force microscopy (AFM) showed no traces of impurity phases. For x = 0.4, excellent microwave dielectric properties (MWD) are obtained with a quality factor (Q × f) of 37,131 GHz at f = 5.2801 GHz, relative permittivity (εr) of 43, and temperature coefficient of resonant frequency (τf) of +1.3 ppm/°C. Variations in εr, Q × f values, and τf may be related to changes in relative density (ρrel), ion polarizability, optical band gap, and tolerance factor, respectively.