Phase, microstructure and microwave dielectric properties of A-site deficient (La, Nd)_2/3TiO₃ perovskite ceramics

(La, Nd)_2/3TiO₃ ceramics were prepared through a conventional solid state mixed oxide route. For phase and microstructure analysis, XRD and SEM were used, respectively. Microwave dielectric properties were measured using a network analyzer. XRD patterns revealed the formation of the parent (La, Nd)_2/3TiO₃ phase along with (La, Nd)₄Ti₉O₂₄ as a secondary phase. The microstructure consisted of rectangular and needle shaped grains, which decreased in size from 4 μm to 2 μm with an increase in sintering temperature from 1300 °C to 1350 °C. Decrease in grain size caused an increase in density of the samples from 4.81 g/cm³ to 5.17 g/cm³. Microwave dielectric properties of the samples calcined and sintered in air atmosphere were ε_r = 40.35, Q × f = 3499 GHz and τ_f = 0 ppm/°C, whereas for a sample calcined in nitrogen and sintered in air they were ε_r = 40.18, Q × f = 4077 GHz and τ_f = +4.9 ppm/°C, respectively.