Electrical Properties Of Thin Films Of Barium Strontium Titanate Ferroelectric Ceramics

Preparation, ferroelectricity and dielectricity of Barium strontium titanate(BST) ceramic and preparation of BST film by PLD are studied in this paper, The main content of this paper are as follows:BaxSr1-xTiO3(x=0.4,0.5,0.65,0.8) ceramics are fabricated with BaCO3, SrCO3, TiO2 as starting material by solid state reaction, characterized by XRD, the result showes that ceramics are perfect perovskite phase, single solid solution structure. Ferroelectrity and dielectricity are tested by ferroelectric analyzer and dielectric analyzer on the condition of room temperature, BaxSr1-xTiO3(x≥0.65)ceramics are ferroelectrity phase, with the increasing of Ba/Sr, coercive electric field and residual polarization of BaxSr1-xTiO3 also increase, dielectric constant decreases with the increasing of frequency, dielectric loss of BaxSr1-xTiO3 increase with the increasing of x, at low frequency dielectric loss of BaxSr1-xTiO3 is large, then decrease gradually with the increasing of frequency, with the frequency larger than 100KHz, dielectric loss of BaxSr1-xTiO3 ceramics are 0≤tanδ≤0.020.Ba0.5Sr0.5Ti1-xCoxO3(x=0,0.002,0.004,0.006,0.008,0.01) ceramics are prepared by solid state reaction as target for pulse laser deposition (PLD), characterized by XRD, the result shows that ceramics are single perovskite structure. can be used for film fabrication. Ba0.5Sr0.5TiO3 film are fabricated on substrate LaAlO3(001), which is c orientation, the optimum technology acquired by changing PLD parameter such as substrate temperature, deposition oxygen pressure, pulse energy and annealing process are substrate temperature 760℃, deposition oxygen pressure 5Pa, pulse energy 350mj, no annealing.Ba0.5Sr0.5Ti1-xCoxO3(x=0,0.002,0.004,0.006,0.008, 0.01) films are fabricated on LaAlO3(001) with optimum technology, the result shows that crystallization quality of Ba0.5Sr0.5Ti1-xCoxO3 film with x=0.01 is the best.Ba0.5Sr0.5TiO3 film are fabricated on substrate LaAlO3(LAO),SrTiO3(STO) and LSAT with previous optimum technology for film deposition on substrate LaAlO3(LAO). Films deposited on STO and LSAT are also c orientation with some additional phase. The lattice mismatch of film deposited on substrate LAO is -5.99%, greatest in three films, negative sign denote that film is subjected to compressive stress in plane. but the FWHM of singleθrocking curve of (002) diffraction peak of BST films grown on the LAO is 0.2409, the minimum in three films, shows the best crystallization quality; Although the lattice mismatch of film deposited on substrate LSAT is -3.26%, the least in three films, the FWHM of singleθrocking curve of (002) diffraction peak of BST film is not the least, so the crystallization quality is not the best. the FWHM of singleθrocking curve of (002) diffraction peak of BST film deposited on STO is 0.5199, the maximum in three films, so the crystallization quality is the worst. Therefore, the optimum technology for BST film deposited on LAO is not the best for the other substrate, so the lattice mismatch is not the most important factors affecting film growth. by optimizing PLD process parameters, to a certain extent, the adverse effects from lattice mismatch on film growth can be eliminated.