Ferroelectric-Dielectric Composites Model of Ba0.5Sr0.5TiO3/Mg2AO4(A = Ti, Si) for Tunable Application

The correspondence between the theoretical model and the experimental results of the dielectric response in two‐phase composites of Ba0.5Sr0.5TiO3 and Mg2AO4 (A = Ti, Si)was studied. The Ba0.5Sr0.5TiO3 (BST50)/Mg2AO4 composites in 2‐2 model structure consisting of BST50 layers and Mg2AO4 layers were fabricated by tape casting and multilayer technique. The 3‐0 model of the two‐phase composites is fabricated by conventional ball mill mixing and solid‐state reaction process. The ceramics samples with dense structure were obtained because the coefficient of thermal expansion (CTE) of Mg2SiO4 (12.84 ppm/°C) and Mg2TiO4 (12.11 ppm/°C) ceramic specimens are close to the pure BST50(13.15 ppm/°C) ceramic. The microstructure, dielectric, and tunable properties of 2‐2 and 3‐0 model composites were investigated. The experimental results agree well with the theoretical prediction in 2‐2 model. An important feature of 2‐2 model composites is that the DC field is efficiently applied to the high‐permittivity ferroelectric phase. With the increase in Mg2AO4 volume fraction q, the tunability of the composite remains almost unchanged whereas the permittivity greatly reduced in the 2‐2‐//model. These results show that the 2‐2‐//model sample is good candidates for the tunable devices.