Abstract:

Ca₂TiO₄+xwt% CaTiO₃ (x=0, 0.8, 1.6 and 3.2) ceramics were prepared by solid state reaction technique. The relation between phase compositions and structures, microstructures, sintering temperatures, and microwave dielectric properties of these ceramic systems were accordingly studied. XRD patterns revealed that the main phase of the undoped CaTiO₃ in Ca₂TiO₄ ceramic systems was closely related with the sintering temperature, and the crystal phase transited from the orthorhombic CaTiO₃ phase (as sintered at 1400℃) to tetragonal Ca₃Ti₂O₇ phase (as sintered at 1420℃). In addition, the CaTiO₃-doping in various amounts resulted in the change of main phase with the sintering temperature increasing from 1420℃ to 1450℃. Wherein, the stability and high-content Ca₃Ti₂O₇ phase could be obtained by doping 1.6wt%-3.2wt% CaTiO₃. The microwave dielectric properties test showed that the undoped Ca₂TiO₄ multiphase systems got a great reduction in the ε_r, Q×f and τ_f values from 59.04, 2340 GHz and 93.13×10^-6/℃ (as sintered at 1400℃) to 59.04, 2340 GHz and 93.13×10^-6/℃ (as sintered at 1420℃), respectively. Additionally, the various amounts of CaTiO₃-doping could keep the Q×f values stably to some extent for the Ca₂TiO₄ ceramic systems.

Key words: layered perovskite, Ca2TiO4, microwave dielectric properties, CaTiO3