Infrared reflectivity and intrinsic dielectric behavior of RETiTaO₆ (RE = Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) microwave ceramics

In this work, we performed infrared reflectivity measurements of RETiTaO₆ dielectric ceramics for rare-earth (RE) = Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb. The infrared spectra were analyzed through the four-parameter semi-quantum model based on two orthorhombic (aeschynite and euxenite) structures presented by the ceramics. We discerned the strongest phonon modes that contribute to the intrinsic dielectric behavior of the two families. Then the unloaded quality factors and the dielectric permittivities were estimated at the microwave region. The variations of the intrinsic dielectric response of both systems with RE ion substitution are discussed in terms of changes in their dielectric polarizabilities. It is proposed that the covalency of the RE–O bonds play an important role in the evolution of dielectric permittivity as well as in the sign of the temperature coefficient of the resonant frequency.