【作者】 贾光；

【导师】 丁士文；

【作者基本信息】 河北大学 ， 无机化学， 2007， 硕士

【摘要】 钛酸钡是电子陶瓷元器件的基础母体原料,被广泛的应用于制备高介电陶瓷电容器、多层陶瓷电容器、动态随机存储器等方面,被誉为“电子陶瓷的支柱”。在BaTiO₃陶瓷材料中加入微量的某些施主元素,其室温电阻率会大幅度下降而成为半导体陶瓷,并且当温度上升到它的居里温度Tc=120℃左右时,其电阻率将急剧上升,变化达5-8个数量级,这种现象称为PTC （positive temperature coefficient）效应。PTC特性是钛酸钡陶瓷的重要性能,利用PTC陶瓷的这一特性,已经制备出了温度补偿元件、温度传感器、过电流保护器等多种电子元器件,广泛地应用于了生产生活的各个方面。本文首先回顾了目前国内外BaTiO₃基PTC瓷粉的研究概况以及各种粉体制备方法,通过分析不同方法的优点和缺点,本文尝试一种全新的合成方法——低温固态反应法来制备纳米BaTiO₃基PTC瓷粉。本方法的优点是：工艺简单,反应时间短,产率高；能耗低；主要反应不使用溶剂；对环境污染小,有很高的工业化价值。用此种方法合成PTC瓷粉在国内外尚未见报道。本实验首先利低温固态反应合成了纯相BaTiO₃粉体。实验过程：量取计算量的TiCl₄,滴加到水中,后加入1：1的氨水调节pH值至7-8。将所得糊状物用去离子水洗涤至无Cl-。取计算量的Ba（OH）₂·8H₂O（Ba/Ti=1）和其他掺杂元素的醋酸盐（La、Y、Nd、Mn等）与TiCl₄在氨水中水解得到的糊状物充分混合,并研磨1h,经100℃烘干后放入马福炉中,800℃焙烧1h,即得到掺杂固溶体粉体固溶体粉体。经XRD物相分析证明,此种方法合成的粉体为立方晶系,掺杂后并没有杂质峰出现。TEM形貌分析,粒子为均匀球形,平均粒径50nm左右。通过制陶实验,研究了不同施主元素（La, Nd, Y等）和受主元素（Mn）对PTC陶瓷材料性能的影响。研究表明,施主元素的加入可有效降低材料的室温电阻,受主元素Mn可以极大的提高材料的升阻比。本文研究了不同施主元素和受主元素的掺杂量对PTC材料室温电阻、升阻比、电阻温度系数等电性能参数的变化规律,并讨论了施受主元素的相互补偿作用,以及各个体系的施受主元素的最佳掺杂量。同时,利用程序可控式无压烧结的方法,讨论了烧结条件（烧结温度、保温时间等）对材料各种电性能的影响,并给予了一定的理论解释,同时确定了各个体系的最佳烧结制度。更多还原

【Abstract】 BaTiO₃, as a kind of very important dielectric material, has been widely used in the production of electric components such as high-property ceramic capacitor, multilayer ceramic capacitor, resonance implement, medium amplifier, and is indispensable in electronic industry. PTCR （positive temperature coefficient of resistivity） property is one of the attractive effects of the semiconducting BaTiO₃, which shows abrupt change （increase） in electrical resistivity at Curie temperature （Tc）. A large number of devices based on the PTCR effect, such as heaters, current limiters and chemical sensors are produced both in the form of a bulk ceramic and film.In this paper, at first, we reviewed the research of the preparation technology of BaTiO₃-based PTCR ceramic powder both home and abroad. By analysing the advantages and disadvantages of other preparation methods, a new and simple method—solid state reaction at low temperature—was employed to prepare nano-BaTiO₃ ceramic powder. Compared with other synthetic techniques, this method exhibits many advantages:no need for solvent, high productivity and selectivity, low energy consumption and simple reaction technology.At first, the pure BaTiO₃ was prepared by solid state reaction at low temperature. A suitable amount of TiCl₄ was slowly added into the deionized water. The pH value of the solution was adjusted to 7-8 by ammonia, and the H₂TiO₃ was formed. Then the Cl^- in H₂TiO₃ must be removed by washing and filtering. The pure H₂TiO₃ and Ba（OH）₂·8H₂O was mixed thoroughly in mortar for 1h at room temperature, then dried at 100℃. The pure BaTiO₃ of cubic phase was prepared in the process of drying at 100℃. Next, the BaTiO₃ -based PTC ceramic powders which were doped different donors and acceptors by acetate were synthesized by this method. A stoichiometrical amount of Ba（OH）₂·8H₂O and different dopant in the form of acetate were mixed and ground with H₂TiO₃ which was produced by hydrolysis of TiCl₄, then dried at 100℃. The doped BaTiO₃ powders were obtained by calcining the precursor for 1h at 800℃. XRD patterns demonstrate that the powders synthesized by this method are cubic perovskite structure, and the figures represent the presence of only BaTiO₃ peaks in the samples with and without additives. TEM photograph shows that the particles of the compounds are uniform and substantially spherical in shape with an average particle size of 50 nm in diameter. The PTC effect of the materials has been studied by preparing ceramics. The influence of various donors （La, Nd, Y） and acceptor （Mn） on properties of PTC materials has been discussed in this article. The resistance at room temperature decreases by doping donor dopant, and the resistance jump increases dramatically by doping Mn. The variations of different donors and acceptors concentration on properties of PTC ceramic materials, such as resistance at room temperature, resistance jump and resistance temperature coefficient, have been studied in detail. Moreover, the effect of sintering conditions （sintering temperature, soaking time） has been discussed and explained to some extent in my opinion, and the optimal sintering conditions of different system are confirmed.更多还原