Dielectric properties of ZrO2-doped (Ba,Sr,Ca)TiO3 ceramics for tunable microwave device applications

ZrO2-doped (Ba0.6 - xSr0.4Cax)TiO3 (BSCT) (x = 0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method, and their structural and dielectric properties were investigated with variation of composition ration and ZrO2 doping content. As the results of X-ray diffraction (XRD) and microstructure analysis, all BSCT specimens showed dense and homogeneous structure without presence of the second phase. The average grain size of samples was decreased with an increase of ZrO2 doping content and the Ba0.4Sr0.4Ca0.2TiO3 specimens doped with 3 wt.% ZrO2 showed a value of 6.8 gm. The Curie temperature and relative dielectric constant were decreased with increasing ZrO2 doping content. The Curie temperature of the Ba0.5Sr0.4Ca0.1TiO3 specimen undoped with ZrO2 showed a maximum value of - 10 degreesC. The relative dielectric constant and the dielectric loss of the Ba0.5Sr0.4Ca0.1TiO3 specimen doped with 3.0 wt.% ZrO2 were about 3300 and 1.12%, respectively The relative dielectric constant was nonlinearly decreased as the field strength is increased. The tunability was increased with decreasing a Ca content and the Ba0.5Sr0.4Ca0.1TiO3 specimen doped with 3.0 wt.% ZrO2 content showed the highest value of 11.57% at 5 kV/cm. (C) 2002 Elsevier Science B.V. All rights reserved.