掺杂浓度对钾镁交替掺杂BST薄膜介电性能的影响

Effect of Doped Concentration on the Dielectric Properties of K and Mg Alternately Doped BST Films

用溶胶-凝胶法(sol-gel)制备掺杂浓度(1~15)mol%的钾和镁交替掺杂钛酸锶钡(BST)薄膜,研究掺杂浓度对薄膜结构和介电性能的影响。X射线衍射(XRD)表明,薄膜为钙钛矿结构。扫描电镜(SEM)显示,薄膜致密、晶粒大小均匀、低浓度下薄膜表面更平整光滑。随着浓度的增加,晶化逐渐减弱,平均晶粒大小和介电损耗呈减小趋势。交替掺杂结合了钾掺杂高调谐率和镁掺杂低介电损耗的优点,明显提高了优质因子。5 mol%对应最佳综合介电性能,在–20~20V范围内,介电损耗小于1.63%,调谐率为40.9%,可满足微波调谐需要。同时,就有关机理进行了讨论。

K and Mg alternately doped BST films with doped concentration of 1 mol%~15 mol% were prepared by a sol-gel method. The influence of the doped concentration on the structure and dielectric properties of the films were studied. X-ray diffraction(XRD) shows that the films exhibit perovskite polycrystalline structure. Scanning electron microscope(SEM) images show that the films are compact and have uniform grain size. The alternately doped films become smoother with decreased doped concentration. With the increase of doped concentration,the crystallization gets weaker,dielectric loss and average grain size tend to decrease. The alternately doped films exhibit higher tunability and lower dielectric loss which combine the advantages of K doped BST films and Mg doped BST films. The figure of merit is also extensively improved. The films with the doped concentration of 5 mol% present the best dielectric properties with dielectric loss less than 1.63% and tunability 40.9%, satisfying the needs of microwave tuned devices. The related mechanism was also analyzed.