MICROWAVE CHARACTERISTICS OF BAO-TIO2 CERAMICS PREPARED VIA A CITRATE ROUTE

Microwave dielectrics of the TiO2-rich BaO-TiO2 system (BaTi4O9 and Ba2Ti9O20) were prepared by the citrate route. Pure and well-crystallized BaTi4O9 and Ba2Ti9O20 particles of nanometer size (30-50 nm) could be obtained by thermal decomposition of citrate gel precursors. After sintering at 1200 degrees-1350 degrees C (for 2-10 h), dense compounds with >90% of theoretical density could be obtained. Dielectric properties of disk-shaped sintered specimens, in the microwave frequency region, were measured in the TE(01 delta) mode, They were found to have excellent microwave characteristics: for BaTi4O9, epsilon(r) = 36, Q = 4900 at 10.3 GHz, and tau(f) = 16 ppm/degrees C; and for Ba2Ti9O20, epsilon(r) = 37, Q = 5300 at 10.7 GHz, and tau(f) = -6.0 ppm/degrees C.