BST 후막의 가변 유전특성과 큐리온도에 관한 연구

The properties of tunable dielectric materials on RF frequency band are important high tunability and low loss for RF variable devices, variable capacitor, phased array antenna and other components application. Various composite of BST(barium strontium titanate) ratio combined with other non-electrical active oxide ceramics have been formulated for such uses. We present the tunable properties and Curie temperature on BST thick films. The grain growth of the weight ratio of BaTiO₃ increased. This can be explained by the substitute Sr²? ion for Ba²? ion in the BaTiO₃ system. The Curie temperature was shifted to lower temperature with increasing SrTiO₃ in the BaTiO₃-SrTiO₃ system, because of decreasing the lattice constant. Also, the dielectric constant, tunability and K-factor of (Ba x Sr 1-x )TiO₃ at over the Curie temperature decreased, at over the 60℃ fixation, maximum dielectric constant at Curie temperature and hence sharper phase transformation occurred at Curie temperature. The result were interpreted as a process of internal stress relaxation resulting form the increase of 90° domains induced the BST. As a result, It is concluded that over the Curie temperature, frequency response and DC field effect for the tunable properties of BST thick film are suppressed by the transition broadening. For the application of tunable devices, that the curie temperature was investigated to be increased.