K and Mg doping effects on structural and dielectric properties in multilayer BST/ST/BST films

摘要

K doped Ba0.6Sr0.4TiO3 (K-BST), Mg-BST, and K&Mg-BST films with multilayer sandwich structures of BST/ST/BST have been designed and prepared by an improved sol-gel method, and pure sandwich-structure BST/ST/BST film is also studied for comparison. Influences of doping on film crystallization, growing behavior and dielectric properties are analyzed. X-ray diffraction (XRD) results exhibit that all films show cubic ABO(3) perovskite structures and mainly grow along (110) orientation. However, better crystallization and smaller average grain size are obtained in doped BST/ST/BST films as compared with pure one. Scanning electron microscopy (SEM) shows that K&Mg doped BST film exhibits the smallest grain size and better uniformity than the pure and other doped BST films. Dielectric properties reveal that all doped films can not only maintain higher tunabilities in sandwich-structure BST/ST/BST films than that in simple BST films, but also exhibit lower dielectric losses and denser surface morphology than that in sandwich-structure BST/ST/BST films, fulfilling the tunable microwave applications.