Dielectric and tunable characteristics of barium strontium titanate modified with Al2O3 addition

The effect of doping Al2O3 on the Ba0.6Sr0.4TiO3 ceramics was investigated. A strong correlation was observed between the average grain size and Al2O3 content. The results indicate that Al3+ behaves as a grain-growth helper below a certain doping level and at the same time lowers the dielectric constant. Both the dielectric loss and tunable properties were modified by the addition of Al2O3.The minimum of the dissipation factor was achieved at Al2O3 doping level up to 0.8 wt.%. The maximum tunablity is 30.1% at the doping level of 0.4 wt.% Al2O3. It was explained by a phenomenological equation that was based on Devonshireʹs theory by the least square method fitting.