High thermal stability of the microwave dielectric properties of CaTi1−x(Nb2/3Li1/3)xO3−δ alloys

Abstract

We report a study of the structural and thermal characteristics of calcium titanate alloys Ca[(Li1/3Nb2/3)xTi1−x]O3−δ (abbreviated as CNLTO). CNLTO alloys were prepared using a new procedure in the solid-state reaction method. Then they were studied using x-ray diffraction, Raman scattering spectroscopy and microwave properties. The symmetry of the atomic structure of the samples belongs to the spatial group Pbnm, showing orthorhombic structure. The microwave dielectric properties of CNLTO for samples ball-milled with the ratios of 1 and 2.4 balls g−1, calcinated at 900 °C (with two different times of exposure: 3 and 5 h) and sintered at 1000 and 1100 °C (during 3 h) were investigated. For both calcination treatments (900 °C, during 3 and 5 h), the dielectric permittivity decreased with decreasing titanium concentration. It was also observed that a higher temperature of calcination contributes to increasing the εr values. Dielectric permittivity values in the range 10–50 were obtained. We noted a decrease in the temperature coefficient of resonant frequency (τf) with an increase of the x value (titanium substitution). CNLTO has excellent microwave properties with τf close to zero for concentrations between 0.925 and 0.950.