Microwave dielectric properties of mixed phase ceramics, Ba(Zn1/3Ta2/3)O3–xCaTiO3 and xMgTiO3–yCaTiO3–z(Nd2O3,wTiO2) |
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Authors: | Takahiro Takada Keisuke Kageyama Mitsuharu Yonemura Naoki Hara Satoshi Takao |
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Affiliation: | (1) Department of Electrical Engineering, National Cheng Kung University, 1 University Rd., Tainan, 70101, Taiwan;(2) Department of Electrical Engineering, National United University, No. 1, Lien-Da, Kung-Ching Li,, Miao-Li, 36003, Taiwan; |
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Abstract: | The effect of different chemical compositions on the microwave dielectric properties of Ba(Zn1/3Ta2/3)O3–xCaTiO3 and xMgTiO3–yCaTiO3–z(Nd2O3,wTiO2) was studied. High fQ dielectrics were designed by optimizing composition and firing conditions. Adding up to 1 mol % CaTiO3 to Ba(Zn1/3Ta2/3)O3 increased εr from 25 to 30 at a firing temperature of 1450 °C, and produced very high fQ values of more than 100 000 GHz at a firing temperature of 1550 °C. EPMA and XRD suggested that ceramics based on Ba(Zn1/3Ta2/3)O3 with CaTiO3 had mixed phases of Ba(Zn1/3Ta2/3)O3 and Ca–Ti–Zn–O. Addition of CaTiO3 increased the Ba(Zn1/3Ta2/3)O3 peak observed in XRD and decreased the Ba3Ta2O8 peak. Prolonged sintering of Ba(Zn1/3Ta2/3)O3 with CaTiO3 increased the fQ value but kept εr constant. 0.5MgTiO3–0.5CaTiO3–z(Nd2O3,wTiO2) showed a high dielectric constant εr>40 and fQ>20 000 GHz. When w=1, τf decreased linearly with z around 0 ppm/ °C in 0.5MgTiO3–0.5CaTiO3–z(Nd2O3,TiO2) (0.25≤z≤0.5). X-ray and EDX analysis revealed a mixed phase matrix of MgTiO3 and (Ca1?αNd2α/3)TiβO3. It was concluded that εr of the high fQ materials Ba(Zn1/3Ta2/3)O3–xCaTiO3 and xMgTiO3–yCaTiO3–z(Nd2O3,wTiO2) would be increased by varying their chemical compositions, x, y, z, and w, and that their fQ value would be improved by appropriate choices of heating temperature and time. |
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