【作者】 李彩玉；

【导师】 张家良；

【作者基本信息】 山东大学 ， 材料物理与化学， 2007， 硕士

【摘要】 本文采用传统的固相反应工艺，分别制备了（Ba，Sr）TiO₃陶瓷，STO-BTO复相陶瓷及BSTO-BTO复相陶瓷。利用扫描电镜和X射线衍射对陶瓷样品的微观结构、结晶结构进行了考查，并对样品的介电温度特性进行了较为详细的研究。（1）采用分析纯的碳酸盐为原料直接配料，利用传统的固相反应工艺，分别在1350℃、1400℃和1450℃烧结温度条件下保温2h制备了一系列的Ba_1-xSr_xTiO₃陶瓷样品。发现各种烧结条件下制备的Ba_1-xSr_xTiO₃陶瓷均是单一相、钙钛矿结构的固溶体，x=0.3是室温下晶体结构从四方相向立方相转化的过渡组分，微观结构随烧结条件和Sr含量有很大的变化。介电测量表明Ba_1-xSr_xTiO₃伴随着温度的变化发生三个相变，三个相变温度在x=0～0.8组分范围内随着Sr含量的增加均呈现出近似线性的下降、并且不依赖于烧结条件。（2）采用两步合成的方法制备了xSTO-（1-x）BTO复合陶瓷样品，烧结温度条件为1275℃、1300℃和1325℃，各保温2h。对XRD谱线的分析表明本实验条件下得到的xSTO-（1-x）BTO陶瓷是以Ba_1-xSr_xTiO₃固溶体为主相，并有少量其它组分的钛酸锶钡杂相存在的复相陶瓷；对SEM图片的分析表明，随烧结温度的升高，相同x值对应的xSTO-（1-x）BTO陶瓷样品晶粒尺寸有所增大，致密性变好：在相同的烧结温度条件下，SrTiO₃含量高的样品气孔明显增多，致密度降低。同一烧结温度条件下，随着SrTiO₃含量的增加，STO-BTO系统的居里温度逐渐向低温方向移动。样品均表现出弛豫特性，居里峰对应的峰值明显小于BSTO固溶体，在居里温度附近介电常数的温度稳定性较BSTO固溶体有所改善。（3）采用两步合成法制备了xBSTO70-（1-x）BTO和yBST080-（1-y）BTO复相陶瓷。研究结果表明，由于保温时间短，复相陶瓷的晶粒尺寸在0.5～1μm左右，且分布均匀。起始两相的选择直接影响到最终复合陶瓷中高低温固溶相的组成，本实验中，相同烧结温度条件下，BSTO80与BTO之间的固溶反应较BSTO70与BTO之间更为显著，这可能是由于BSTO80与BSTO70相比同BTO之间有更大的离子浓度差的缘故。实验中所有配比的复相陶瓷的介电温谱均呈现双峰结构。在1300℃／10min的烧结温度条件下，组分为0.7BSTO70-0.3BTO，0.8 BSTO70-0.2BTO和0.7BST080-0.3BTO的复合陶瓷分别在-70℃～10℃、-80℃～0℃和-120℃～20℃的温度范围内表现出了良好的介电温度稳定性。更多还原

【Abstract】 A series of （Ba,Sr）TiO₃ ceramics, STO-BTO composite ceramics and BSTO-BTO composites were prepared by conventional solid-state reaction method. Temperature dependence of dielectric constant was measured. Crystal structure and microstructure were analyzed through X-ray diffraction patterns and scanning electron microscope photographs of the samples, respectively.（1） Ba_1-xSr_xTiO₃ ceramics were prepared by the conventional solid-state reaction method at sintering temperatures of 1350℃, 1400℃and 1450℃for 2 h, respectively. XRD analysis confirms that all of the BST ceramics are the good solid solution with the monophase of perovskite crystal structure. At room temperature, BST ceramics show a change of crystal structures from the cubic phase to the tetragonal one at x=0.3. Microstructures change significantly with both Sr content and sintering temperature. For those compositions with x=0⁰.8, there are three phase transitions, which temperatures decrease linearly with Sr content and are independent of sintering temperature. Dependence of dielectric peak values on Sr content and sintering temperature is discussed.（2） xSTO-（1-x）BTOcomposite ceramics were prepared by a two-step synthesis method at sintering temperatures of 1275℃1300℃and 1325℃for 2 h, respectively. XRD analysis confirms that all of the xSTO-（1-x）BTO samples have main phases of Ba_1-xSr_xTiO₃ solid solution crystal structure , a small amount of other components of barium strontium titanate phases are also exist in the composite ceramics. Microstructures change significantly with both Sr content and sintering temperature. For the samples at same sintering temperature, the Curie temperature gradually shifts to low temperature with increasing STO content. All samples show relaxation properties, the Curie peak values are significantly less than BSTO solutions.（3） xBSTO70-（1-x）BTO and yBSTO80-（1-y）BTO composites were prepared by a two-step synthesis method. Study results show all the samples have the grain size of 0.5 -1 μm; with the sintering temperature increases, the density of the samples has improved. The diffusion between BSTO80 and BTO is more notable than that between BSTO70 and BTO. This is probably because the ion concentration difference of BSTO80 and BTO is larger than that of BSTO70 and BTO. The ε’-T spectrum of the composites shows bimodal structure. In the sintering condition of 1300℃/10min, the 0.7BSTO70-0.3BTO, 0.8 BSTO70-0.2BTO and 0.7BSTO80-0.3BTO composites show a good dielectric temperature stability in the temperature range of -70℃--10℃, -80℃-0℃ and -120℃--20℃, respectively.更多还原