Tailoring the crystal distortion and dielectric properties of 0.7CaTiO3-0.3NdAlO3 microwave ceramics by La, Sm and Eu doping into A-site Nd

The TiO6 octahedra titling and rotation play an important role in affecting the microwave properties of 0.7CaTiO3-0.3NdAlO3 microwave ceramics by A-site La, Sm and Eu doping. The oxygen octahedra of Sm-doped 0.7CaTiO3-0.3NdAlO3 ceramics exhibit antiphase tilting, while both in-phase and antiphase tilting coexist in the 0.7CaTiO3-0.3EuAlO3 ceramics. There is an undeniable correlation between the crystal distortion and the tolerance factor t. As the tolerance factor t continues to increase, the crystal structure of A-site doped CTNA ceramics changes from both in-phase tilting and antiphase tilting to untilted structure and the TiO6 octahedra exhibits an inclination to tilt around c axis. The weakening bending vibration of the Ti–O(2)-Ti bond results in the increase of the polarization and the damping coefficient of lattice vibration. The dielectric constant (εr) rises to 48 from 43 and Q × f values decrease to 36,000 GHz from 44,800 GHz (measured at 6 GHz). These findings could be used to guide the tailoring of the crystal distortion and microwave dielectric properties of technologically important perovskite 0.7CaTiO3-0.3NdAlO3 based ceramics.