Phase composition and microwave dielectric properties of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics with alumina addition

Ca0.128Ba0.032Sm0.46Li0.3TiO3-x wt.% Al2O3 microwave dielectric ceramics with temperature stability were prepared by the traditional solid-state reaction method. The effects of Al2O3 doping on phase composition, micromorphology, and microwave dielectric properties of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics were investigated. X-ray diffraction results showed that no other phase was introduced by doping, and the diffraction peaks of all the ceramics could be indexed by standard JCPDS cards of No.42−0423 (CaTiO3) and No.43−0235 (BaSm2Ti4O12). To further study the effects of Al2O3 doping on microstructure and lattice vibration of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics, the structural refinement and Raman spectroscopy techniques were also adopted. Doping Al2O3 decreased the lattice constant of CaTiO3-phase solid solution, modified the morphology and improved microwave dielectric properties of the ceramics. When sintered at 1300 °C for 4 h, the ceramics with 0.9 wt.% Al2O3 showed excellent microwave dielectric properties: εr = 87.9 ± 0.4, Q × f = 6671 ± 103 GHz, and τf = -1.2 ± 0.9 ppm/℃.