Tunable Dielectric Properties and Curie Temperature with BST Thick Films

BST 후막의 가변 유전특성과 큐리온도에 관한 연구

  • 김인성 (한국전기연구원 전자기소자연구그룹) ;
  • 송재성 (한국전기연구원 전자기소자연구그룹) ;
  • 민복기 (한국전기연구원 전자기소자연구그룹) ;
  • 전소현 (경남대학원 대학원 신소재공학과)
  • Published : 2006.08.01

Abstract

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 $BaTiO_3$ increased. This can be explained by the substitute $Sr^{2+}$ ion for $Ba^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$in the $BaTiO_3-SrTiO_3$ system, because of decreasing the lattice constant. Also, the dielectric constant, tunability and K-factor of $(Ba_xSr_{1-x})TiO_3$ at over the Curie temperature decreased, at over the $60^{\circ}C$ 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 $90^{\circ}$ 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.

Keywords

Tunable Dielectrics;BST

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