Microwave Dielectric Properties of Doped BaTi 4 O 9

Polycrystalline BaTi 4 O 9 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, τ f , of ∼37, 5675, and 15 ppm/°C, respectively, were determined at 4 GHz for undoped BaTi 4 O 9 . Doping did not significantly affect k and τ 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% MnO 2 as a second phase improved Q from 3675 to 7600.