Crystal structure and temperature dependence of permittivity in barium aluminate based solid solutions

Abstract

AbstractThis study systematically investigated the structural, dielectric, and ferroelectric properties of BaAl(2−2x)(Mg0.5Ti0.5)2xO4 ceramics in the 0 ≤ x ≤ 0.04 range. Single‐phase solid solutions in the P63 space group with hexagonal crystal symmetry were confirmed in the composition range of 0 ≤ x ≤ 0.03. The bond lengths of Al1/(Mg,Ti)–O, Al2/(Mg,Ti)–O, and Al3/(Mg,Ti)–O increased with the increase in x, as confirmed through the Rietveld refinement and evolutions of corresponding modes in Raman spectra. The temperature stability of dielectric properties improved at a composition around x = 0.03, and the dielectric constant εr ascended with the increase in x. Ultrabroad temperature stability (−100°C to 700°C) was obtained, and an optimal combination (εr = 18.5, tan δ < 10−3, −22 ppm/°C ≤ TCC ≤ +20 ppm/°C, resistivity ~4.5 × 1014 Ω·cm) was achieved for the x = 0.03 ceramic sintered at 1260°C in air for 6 hours. The increase in stability was ascribed to the variations in axial bonds, and lattice distortions were determined through high‐resolution transmission electron microscopy. The x = 0.03 ceramic could be a promising candidate for C0G or NP0 multilayer ceramic capacitors because of its low loss, high reliability, superior insulating properties and comparatively low‐cost raw materials.