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Effects of La0.5Sr0.5CoO3 sol concentration on the microstructure and dielectric properties of Ba0.6Sr0.4TiO3 films prepared by sol-gel method on Ti substrate Dan Jiang1, Songwei Han1, Xuelian Zhao1 and Jinrong Cheng1* School of Materials Science and Engineering, Shanghai University, Shanghai 200072 *corresponding author: [email protected]

ABSTRACT Ba0.6Sr0.4TiO3 (BST) thin films were deposited on La0.5Sr0.5CoO3 ᧤LSCO᧥buffered Ti substrates. Both BST and LSCO were prepared by sol-gel method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used to investigate the effect of LSCO sol concentration on the crystallinity and surface morphology of the films. The results show that with the increase of LSCO sol concentration, BST films show variation of the structure and dielectric properties. BST films for LSCO of 0.2 mol/L exhibit a better crystallinity and improved dielectric properties, with the tunability, dielectric constant and tanį of 30%, 420 and 0.028 respectively. INTRODUCTION Ba1íxSrxTiO3 (BST) is one of the candidates for tunable microwave devices for wireless telecommunications [1,2] for its highly nonlinear dielectric response and high tunability in the vicinity of the paraelectric to ferroelectric phase transformation temperature Tc [3], Usually, BST thin films have been deposited by radio frequency (RF) sputtering [4], pulsed laser deposition (PLD) [5], metal organic chemical vapour deposition (MOCVD) [6] and sol-gel method [7]. Compared with other methods, the sol-gel method has several advantages due to its simplicity, easy control of the film composition, low cost of the apparatus and raw material [8]. Usually, platinized silicon is employed as substrate for BST thin films. However, some problems existed, such as the formation of hillocks in Pt electrode at high temperature [9] and the diffusion between electrode and Si, which greatly undermine the dielectric properties and hinder practical applications of BST thin films [10]. Recently, depositing BST thin films directly on base metal substrate have attracted much attention for their advantages of mechanical flexibility of the substrate and low cost. However, the low oxidation resistance of base metal substrates is one of the principal limitations in preparing BST films on metal substrates, which caused diffusion or reaction between the films and the substrates in the process of heat treatment [11]. LSCO, which has a pseudocubic perovskite structure with a lattice constant of 0.3835 nm [12] has been used as buffer layer. There are high lattice match and structural compatibility for the BST/LSCO structures, which are potential to improve dielectric properties of the films on base metal substrates. Recently, BST thin films on Ti substrates with LSCO buffer layers have been few reports. In this study, BST films were prepared on Ti substrates by sol-gel method with LSCO buffer layers. The effect of the LSCO sol concentration on dielectric properties of BST films was investigated. EXPERIMENT The LSCO sol were prepared by using la