Effect of annealing on the microwave properties of (Zr,Sn)TiO4 ceramics

(Zr,Sn)TiO4 dielectric ceramics containing La2O3 and NiO as sintering aids were prepared by the conventional solid-state reaction. Ceramics sintered at 1370°C for 20 h exhibit dielectric constants k around 37.1 and a QF value of 41,500 GHz, measured at 4 GHz. After annealing, k remains constant. However, the QF value is strongly affected by the annealing process. At 1300°C, annealing has no effect on the quality factor Q. Annealing at temperatures 1225 and 1200°C induce a ≈50% decrease of QF values. Intermediate annealing temperatures of 1275 and 1250°C induce a ≈25% improvement of QF values. These ceramics were investigated by XRD, SEM and EDS. The matrix phase ZST was observed together with three different secondary phases: TiO2ss, La2/3TiO3 and TiNiO3. Appearance and following diffusion of these secondary phases and other impurities to the ceramic surfaces during annealing can explain the QF behaviour.