烧结温度和CaTiO_3添加对不稳定层状Ca_(n+1)Ti_nO_(3n+1)(n=1)陶瓷体系结构与介电性能的影响

Influence of Sintering Temperature and CaTiO_3 Doping on Structure and Dielectric Properties for Instability Layered Ca_(n+1)Ti_nO_(3n+1)(n = 1) Ceramics

采用固相反应法制备了Ca_2TiO_4+xwt%CaTiO_3(x=0、0.8、1.6和3.2)陶瓷,并分析了其相组成与结构、显微结构、烧结温度和微波介电性能之间的影响关系。室温XRD晶体结构分析表明:未掺杂CaTiO_3的Ca_2TiO_4体系主晶相受烧结温度的影响明显,由1400℃烧结的正交结构CaTiO_3相转变为1420℃烧结的四方结构层状Ca_3Ti_2O_7相。当烧结温度由1420℃升高至1450℃时,不同含量CaTiO_3掺杂均能使Ca_2TiO_4体系中主晶相的含量和成分发生改变。其中,1.6wt%~3.2wt%的CaTiO_3掺杂可使Ca_2TiO_4体系获得稳定且含量较高的Ca_3Ti_2O_7相。微波介电性能测试结果显示,未掺杂的Ca_2TiO_4体系的ε_r、Q×f和τ_f值均在其主晶相发生改变时大幅降低,分别由1400℃烧结的85.84、10030 GHz和508.87×10^(-6)/℃降至1420℃烧结的59.04、2340 GHz和93.13×10^(-6)/℃,而不同含量的CaTiO_3掺杂则可在一定范围内稳定复相Ca_2TiO_4体系的Q×f值。

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 εr, Q×f and τf 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.