Dielectric and mechanical characteristics of lanthanum aluminate ceramics with strontium niobate addition

The microstructures, microwave dielectric properties and mechanical properties were investigated for LaAlO3 ceramics with Sr2Nb2O7 additive. The grain size decreased significantly when the additive was introduced, and the Sr2Nb2O7 reacted with the LaAlO3 ceramic matrix to form a LaNbO4 secondary phase. The dielectric constant varied slightly, while the Qf value increased at first and then decreased when the additive content passed a critical value. The effects of the Sr2Nb2O7 additive upon the temperature coefficient of resonant frequency were dependent on the sintering conditions. The fracture toughness was significantly improved by Sr2Nb2O7 addition.