Citrate route to Sn-doped BaTi4O9 with microwave dielectric properties

Highly reactive and nanometer-sized (30-50 nm) Sn-doped BaTi4O9 (BaTi(4-)xSn(x)O(9); x = 0.0-0.03) powders have been prepared by the citrate-precursor method. The effect of Sn substitution on the crystallization and microwave dielectric properties has also been investigated on the basis of microstructure and crystal structure. Addition of a small amount of SnO2 resulted in a lowering of the sintering temperature of BaTi4O9, and at 1250-1300 degrees C for 2-5 h, dense compounds with a theoretical density up to 99% could be obtained. The Sn-doped BaTi4O9 materials were found to have excellent microwave dielectric properties with epsilon(r) = 34-37, Q = 8300-8900 at 11 GHz and tau(f) = 3.6-16.1 ppm/degrees C.