Study on Microstructures and Dielectric Properties of Barium Strontium Titanate Ceramics Co-Doped Al2O3-MgO

The Ba(0.6)Sr(0.4)TiO(3) (BSTO) ceramics were prepared by traditional electrical ceramic methods. Effects of co-doping low dielectric constant oxides Al(2)O(3) and MgO on microstructures and dielectric properties of Ba(0.6)Sr(0.4)TiO(3) ceramics were investigated. The results show that BSTO/MgO/Al(2)O(3)(BMA) ceramics can be sintered at 1350 similar to 1450 degrees C. The main crystal phases are Ba(0.6)Sr(0.4)TiO(3) and MgAl(2)O(4). Al(3+) is easier to enter Ba(0.6)Sr(0.4)TiO(3) lattice in the replacement of Ti(4+) than Mg(2+). When Al(2)O(3) content exceeds 25wt%, Al(2)O(3) will react with BaAl(2)O(4) to generate a new phase BaAl(12)O(19). Proper amount of Al(2)O(3)-MgO can reduce the dielectric constant of BSTO ceramics which also can ensure the higher tunability. There is obvious frequency dispersion characteristic in BMA ceramics with the increase of Al(2)O(3). When Al(2)O(3) content exceeds 25wt%, two dielectric peaks are observed in the temperature spectrums of ceramics, which decrease and broaden. When Al(2)O(3) content is 20wt%, the tunability amounts to 33.9% under a bias field of 1.0kV/mm dc.