MICROWAVE DIELECTRIC-PROPERTIES OF DOPED BATI4O9

Polycrystalline BaTi4O9 doped with Mn, Sn, Zr, Ca, Sr, and Pb was prepared from carbonates and oxides. Single-phase ceramics with densities exceeding 97% of theoretical were made with up to 3 mol% Mn; 6 mol% Sn, Zr, and Ca; and 8 mol% Sr and Pb. Dielectric constant, k, quality factor, Q, and temperature coefficient of frequency, tau-f, of approximately 37, 5675, and 15 ppm/degrees-C, respectively, were determined at 4 GHz for undoped BaTi4O9. Doping did not significantly affect k and tau-f. However, doping with Mn, Sn, and Pb lowered Q, whereas doping with Zr, Ca, and Sr increased Q by up to 2000. Additions of 0.5 mol% MnO2 as a second phase improved Q from 5675 to 7600.