Effect of NiO and Al2O3 on the Curie temperature, microstructure, and dielectric properties of Ba0.5Sr0.5TiO3 ceramics

A series of new x(yNiO/zAl(2)O(3))-(1-x)Ba0.5Sr0.5TiO3 (x = 10, 30, and 50 wt.%, y = 1, 1.3, 1.5, z = 1, 1.3, and 1.5 mol) ceramics were prepared using the solid-phase method. The effects of the spinel oxides on the microstructure, lattice vibrations, and dielectric properties of Ba0.5Sr0.5TiO3 were assessed. When NiO and Al2O3 were present in equal quantities, they reacted to form NiAl2O4. Under the recombination effect, the dielectric permittivity of Ba0.5Sr0.5TiO3 was effectively reduced, the Curie temperature (T-c) was increased, and tunability gradually increased. The T-c value was not significantly altered when NiO was in excess. Impurity phases were generated, and the T-c value decreased when Al2O3 was in excess. This study elucidated the unique role of the spinel structure. The 50 wt.%(NiO/Al2O3)-50 wt.%Ba0.5Sr0.5TiO3 had excellent microwave dielectric properties, with dielectric permittivity, tunability, and Q values of 300, 18.7%, and 357, respectively.