Microstructural evolution, dielectric performance, and densification behavior of novel NaAGeO4 (A = Sm, Y) ceramics

Novel NaAGeO 4 (A = Sm, Y) ceramics with olivine structures were prepared and characterized. The phase composition, microstructural evolution, and densification behavior of the ceramics were investigated. The NaAGeO 4 (A = Sm, Y) ceramics possessed a single orthorhombic crystal system with Pbn21 and Pnma space groups. The NaSmGeO 4 ceramics had dense grains, clear boundaries, and low sintering temperatures, whereas a relatively wide range of sintering temperatures were feasible for the NaYGeO 4 ceramics. The NaSmGeO 4 ceramic material sintered at 1025 °C possessed excellent performance-related parameters, i.e., Q × f = 31,281 GHz, ε r = 6.29, and τ ƒ = −48.3 ppm/°C, whereas those for the NaYGeO 4 ceramic material were Q × f = 32,646 GHz, ε r = 6.74, and τ ƒ = −39 ppm/°C at 1200 °C. Furthermore, doping the NaYGeO 4 ceramic material with CaTiO 3 to obtain 0.12CaTiO 3 -0.88NaYGeO 4 yielded a τ ƒ value close to zero (−3 ppm/°C). The results demonstrate that NaAGeO 4 (A = Sm, Y) ceramics have substantial potential for application in microwave devices.