Preparation of (Ba_1-x, Sr_x)TiO₃ Thin Films on Glazed Alumina Substrate and Improvement of Temperature Dependence of Dielectric Properties

In this study, (Ba1-x,Srx)TiO3 thin films of various composition ratios were deposited on glazed Al2O3 substrates by the CSD method, and the temperature dependence of the dielectric property was analyzed. The dielectric property of the BST (80/20) thin film annealed at C was highly tunable, and the temperature dependence of the dielectric constant was stabilized at around room temperature. However, this BST (80/20) thin film exhibited intense ferroelectricity. Its tan intensified to 0.0511 in the high-frequency range (1 MHz). After the BST thin film was annealed at 600C, the grain size of the BST thin film was reduced to 40 nm and the ferroelectricity was alleviated. The dielectric constant, tan, and tunability of the BST thin film at 100 kHz were 158, 0.0170, and 39.6 (214 kV/cm, 6.0 V), respectively. The change rate of the dielectric constant, which indicates its temperature dependence, was ±7 or less in the range of -55 to 85C. Therefore, this BST thin film was considered to guarantee a wide operation temperature range for microwave tunable devices.