Dielectric properties of (1 - x)NdGaO₃-xCaTiO₃ solid solution at microwave frequencies

Microstructure and microwave dielectric properties of (1 -x)NdGaO₃-xCaTiO₃ ceramics have been investigated. Crystal structure of all the specimens was orthorhombic and the lattice parameters decreased with an increase of x. For specimens with x ≤ 0.5, a Nd₃Ga₅O₁₂ phase was observed. The Q value of Nd₃Ga5O₁₂ ceramics was about 10,000 at 12 GHz and the dielectric constant (∈_r) was about 12. A liquid phase was found in the specimens with x ≥ 0.5, containing a high concentration of Ca and Ga ions. The dielectric constant and the temperature coefficient of resonant frequency (τ_f) of the specimens increased with an increase of x. The Q × f value of the NdGaO₃ specimen was about 85,000 GHz and it decreased inversely with x. Excellent microwave dielectric properties of Q × f = 46, 000 GHz, ∈_r = 45 and τ_f = -2.0 ppm/°C were obtained for (1 - x)NdGaO₃-xCaTiO₃ ceramic.