As a microwave dielectric, BaTi4O9 is profitable for its high Q (quality factor; 1/tan δ), but is disadvantageous for its high τf (temperature coefficient of resonant frequency). In this investigation, ZnO-Ta2O5 system compounds with negative temperature coefficients were added to BaTi4O9 to study their effects on the dielectric properties.
The dielectric properties of BaTi4O9 were improved by ZnO and Ta2O5 additions, and the best composition obtained was as follows; BaO:17.50 mol%, TiO2:70.00 mol%, Ta2O5:0.75 mol% and ZnO:11.75 mol%. The microstructure was composed of two different phases; one was the black phase with poor Zn and the other was the white phase with rich Zn, and it was confirmed that the former was denoted as BaTi4O9 containing 0.944 mol%Ta2O5 and the latter as BaO(ZnO)2(TiO2)4 with 0.633 mol%Ta2O5, respectively. The color of cross-sectioned specimen differed by the positions, i.e., it was light brown at the edge and grey at the center. The specimen, however, showed uniform dark brown both in the center and on the surface by the addition of Mn2O3, where the most suitable amount of Mn2O3 to be added was 0.18 mol%.
(Received December 4, 1991)
Keywords: microwave dielectrics, dielectric property, BaTi4O9, addition of ZnO-Ta2O5, addition of Mn2O3, Q value, temperature coefficient
† Graduate Student, Osaka University.