节点文献
钛酸锶钡铁电陶瓷的电性能研究及其薄膜制备
【作者】 马维云；
【导师】 张鹏翔；
【作者基本信息】 昆明理工大学 ， 材料学， 2010， 硕士
【摘要】 本论文就钛酸锶钡(BST)铁电材料陶瓷制备及其铁电,介电性能,薄膜的PLD制备工艺方面进行了一些基础研究。本论文主要内容有：以BaCO3, SrCO3, TiO2为原料,采用传统固相烧结法制备了BaxSn1-xTiO3(x=0.4,0.5,0.65,0.8)系列陶瓷,利用XRD对其进行了表征,经分析可知所制备样品为完全的钙钛矿相,单一的固溶体结构。利用铁电分析仪,阻抗分析仪分别测试了样品的铁电性能和介电性能。在室温时,x≥0.65时BaxSr1-xTiO3陶瓷是铁电相；随着Ba/Sr比例的增加,BaxSr1-xTiO3的矫顽电场和剩余极化强度也增加；BaxSr1-xTiO3陶瓷材料的介电常数随频率变化是呈下降的趋势的；随着x值的增大,BaxSr1-xTiO3陶瓷的介电损耗数值也增加。在低频时各样品的介电损耗值很大,随着频率的增加,各样品的介电损耗值逐渐减小,在频率大于100KHz后,BaxSr1-xTiO3系列陶瓷的介电损耗在0≤tanδ≤0.020。采用传统固相反应法制备了掺杂Co的Ba0.5Sr0.5Ti1-xCoxO3(x=0,0.002,0.004, 0.006,0.008,0.01)系列陶瓷作为脉冲激光沉积(PLD)钛酸锶钡(BST)薄膜的靶材,利用X射线衍射(XRD)分析,靶材基本形成了单相的钙钛矿结构,满足制备薄膜的要求。首先在LaA103(LAO)衬底上制备了呈c取向的Ba0.5Sr0.5TiO3薄膜,通过改变衬底温度,生长氧压,脉冲激光能量等PLD系统参数并结合退火工艺,探索出LaAlO3(LAO)衬底上Ba0.5Sr0.5TiO3薄膜生长的最佳条件为：衬底温度760℃,生长氧压5Pa,脉冲激光能量350mj,不退火。利用最佳条件在LaAlO3(LAO)衬底上制备了掺杂Co的Ba0.5Sr0.5Ti1-xCoxO3 (x=0,0.002,0.004, 0.006,0.008,0.01)薄膜,结果表明x=0.01时薄膜结晶质量最好。利用在LaAlO3衬底上制备Ba0.5Sr0.5TiO3薄膜的最佳条件在LaAlO3(LAO)、SrTiO3 (STO)和LSAT单晶衬底上制备出Ba0.5Sr0.5TiO3薄膜,在LSAT,STO衬底上制备的薄膜均呈c取向,但产生一些杂相,虽然LAO衬底和薄膜的失配度最大,达到了-5.99%(负号表示薄膜在面内受到压应力),但是在LAO衬底上生长的BST薄膜(002)衍射峰单0摇摆曲线半高宽最小,达到0.2409,结晶质量最好；LSAT衬底与薄膜晶格失配度最小,为-3.26%,但LSAT衬底上生长的薄膜(002)衍射峰单θ摇摆曲线半高宽并不是最小,即结晶质量并不是最好的,STO衬底上生长的薄膜(002)衍射峰单0摇摆曲线半高宽达到0.5199,结晶质量最差。因此在LAO衬底制备BST薄膜最佳条件并不一定适合其他衬底,衬底与晶格的失配度并不是影响薄膜生长的最主要因素,通过优化PLD工艺参数,在一定程度上可以消除失配度对薄膜生长造成的不利影响。
【Abstract】 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.