Dielectric and tunable properties of bulk columnar Ba0.6Sr0.4TiO3/MgO composites

Ba 0.6 Sr 0.4 TiO 3 (BST)/MgO columnar composites are fabricated via the spark plasma sintering (SPS) method. The microstructure, dielectric and tunable properties of columnar composites are investigated. The unmodified BST Curie temperatures with the increase of MgO addition indicate a sufficient suppression of ions interdiffusion between the two phases. The dielectric constant is decreased from 7000 to 3800 when MgO weight ratio is up to 15% while the tunability still stays at high level over 45%. The coefficient of the dielectric nonlinearity β shows a growing trend with increasing MgO content. The experimental results are in agreement with the theoretical prediction and confirm that if the composite is fabricated in columnar model, a reduction of dielectric constant without a deterioration of tunability could be achieved, which make them useful for potential tunable device applications in wireless communication system.