【作者】 周申；

【导师】 于军；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2007， 硕士

【摘要】 ABO₃型钙钛矿结构铁电体钛酸锶钡（BaxSr1-xTiO₃、BST）材料具有较高的相对介电常数、较低的插入损耗、以及介电常数在直流电场下显著的非线形特性行为,被公认为是制备相控阵微波移相器的理想材料。本文主要研究了A位Ba²⁺部分取代的(Ba_0.7-xPb_x)Sr_0.3TiO₃陶瓷的结构特性与电学特性。本文采用固相反应法制备了ABO₃型化合物Ba0.7Sr0.3TiO₃、以及Pb²⁺对A位Ba²⁺部分取代的(Ba_0.7-xPb_x)Sr_0.3TiO₃ （x=0.1～0.4）陶瓷,研究了其结构、铁电与介电特性。XRD分析表明,随着Pb²⁺对Ba²⁺取代程度的加强,样品逐渐由立方相过渡到四方相,c轴和a轴晶格常数偏离相应增大,晶格畸变程度明显加剧。ESEM分析表明随着样品烧结温度的升高,陶瓷晶粒逐渐长大;Pb的掺入使样品更加致密,孔洞大量减少,晶粒细化,而当Pb含量较大时,由于高温下Pb挥发严重,使得陶瓷样品会产生少量第二相且使陶瓷样品的孔洞增多。铁电性能测试发现,当x≤0.3时,样品的电滞回线形状平滑饱和,随着Pb浓度的提高,BST陶瓷的铁电性能逐渐增强,剩余极化相应增大。(Ba_0.4Pb_0.3)Sr_0.3TiO₃与BST相比极化Ps值由8.268μC/cm²增大到15.698μC/cm²,剩余极化Pr值由4.115μC/cm²增大到11.300μC/cm²,矫顽场由2.183 kV/cm增大到9.470 kV/cm。介电特性测试表明,随着Pb取代程度的加强,样品的居里温度逐渐升高,介电常数逐渐减小、且变化趋于平缓,说明室温下样品处于更稳定的铁电相。与纯BST相比,Pb²⁺部分取代后样品的介电损耗均有所降低。更多还原

【Abstract】 Ferroelectric materials such as Barium strontium titanate (Ba_xSr_1-xTiO₃, BST) with ABO₃ type perovskite structure have gained much attention for their superior performance. They are considered as a kind of the most important materials which have great potential perspective in field of microwave、micro-electronics and memories. Nowadays, Ba_xSr_1-xTiO₃ has been recognized as one of the most ideal materials for microwave phase shift fabricating because of its high dielectric constant, lower loss tangent and remarkable nonlinear properties.In this paper, the Ba_0.7Sr_0.3TiO₃ and (Ba_0.7-xPb_x)Sr_0.3TiO₃ （x=0.1～0.4, BPST） compounds with a structure of ABO₃ were synthesized by conventional solid reaction method. Influence of Pb²⁺ substitute for Ba²⁺ in A-site on the sintering behavior and the dielectric and ferroelectric properties of BST/BPST ceramics were investigated. The X-ray diffractometry （XRD） patterns analysis reveals that the samples change from tetragonal to cubic system, and more dramatical structural distortion have been observed with the increase of Pb²⁺ concentration. The Environment Scanning Electron Microscope （ESEM） micro-graph indicate that the grain size of BST ceramics grows with the increase of sintering temperature. The smaller grain size and more compact structure of the Pb²⁺ substituted samples can be observed clearly in the ESEM graphics. The ferroelectric properties analysis shows saturated hysteresis loops of the samples when x≤0.3, which indicates the improvement of their ferroelectric properties. Compared with the ferroelectric parameters such as saturate polarization （Ps）, remnant polarization （Pr） and coercive field （Ec） of BST, (Ba_0.4Pb_0.3)Sr_0.3TiO₃ has a superior performance of 15.693μC/cm², 11.300μC/cm² and 9.470 kV/cm, respectively, while the accordingly values of BST are 8.268μC/cm², 4.115μC/cm² and 2.183 kV/cm. The dielectric properties analysis reveals that the Tc increases gradually with the enhancement of Pb substitution. At room temperature, the decrease of dielectric constant becomes smaller with the Pb content increase, which i validate a relative static ferroelectric phase of the high Pb content samples. Besides, the loss tangent of the samples which are substituted by Pb²⁺ is lower than that of pure BST.更多还原