Formation and Microwave Dielectric Properties of Complex Perovskite Ca(Ga1/2Ta1/2)O3

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Abstract
In order to prepare a(1:1) complex perovskite compound for microwave dielectric resonators in the system CaO-Ga2O3-Ta2O5, phases present and microwave dielectric properties of the ternary dielectrics with various compositions near the stoichiometric cation ratio (4CaO⋅Ga2O3⋅Ta2O5) have been investigated. X-ray diffractometry combined with elementary analysis using WDX revealed that the dielectric materials prepared from a stoichiometric powder mixture of Ga2O3, Ta2O5 and CaCO3 are composed of the intended Ca(Ga1/2Ta1/2)O3 complex perovskite phase (CGT). It was also demonstrated that some other phases are formed in sintered samples with compositions different from the stoichiometric CGT ratio. The phase relation near the CGT composition is proposed, which contains newly obtained ternary (4CaO⋅2Ga2O3⋅Ta2O5) and binary (CaO-Ta2O5) compounds. A microwave high Q value of the CGT sample is found to be affected considerably by the secondary phases, with a pronounced deleterious effect by the binary compound. Additionally, some factors which might cause a marked decrease in the microwave Q value of the CGT sample on prolonged sintering are discussed in relation to structural evolution during sintering.

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