Lead Free CaTiO₃-Based Ceramics: Sintering, Phase Transitions and Dielectric Properties

Abstract

Various chemical compositions (1-x)CaTiO3+xMgF2+xLiF were prepared and dry-ground. The powder mixtures were pressed to pellets and co-fired at 900°C for 2h. The obtained ceramics were investigated by XRD, SEM, DSC and dielectric measurements. A new solid solution with nominal composition Ca1-xMgx(Ti1-xLix)O3-3xF3x occurred in the initial composition range 0 ≤ x ≤ 0.25. The fluoride additive MgF2+LiF lowered significantly the sintering temperature of pure CaTiO3. Above room temperature, one or two second order phase transitions were detected by DSC and confirmed by dielectric measurements. Moreover, below room temperature, a frequency peak dependent on the permittivity and losses was observed and the quantum paraelectric behaviour of CaTiO3 disappeared with increasing x. These oxifluorides could be of interest for electronic applications.