Dielectric properties of barium strontium calcium titanate ceramics for a microwave phase shifter

(Ba0.6-xSr0.4Cax)TiO3 (BSCT, x=0.10, 0.15, 0.20) specimens were fabricated by using the conventional mixed oxide method. The results of X-ray diffraction and microstructure analysis showed that all the BSCT specimen's had a dense, homogeneous structure. The BSCT(50/40/10) specimen sintered at 1500 degreesC showed the highest average grain size (18.25 mum). The Curie temperature and the relative dielectric constant at room temperature decreased with increasing Ca content. The Curie temperature of the BSCT(50/40/10)- specimen showed a maximum value of -10 degreesC. The relative dielectric constant and the dielectric loss of the BSCT(50/40/10) specimen, which was sintered at 1450 degreesC and measured at 1 kHz, were about 4324 and 0.972 %; respectively. The tunability increased with increasing Ca content, and the BSCT(50/40/10) specimen sintered at 1450 degreesC showed a good value of 5.4 % at 4 kV/cm.