【作者】 张妍；

【导师】 李伟力；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2015， 硕士

【摘要】 巨介电常数通常意味着材料具有高储能的密度,而高储能密度是影响电容器,探测器,信息存储器等电子元器件优良的重要因素。因此研究巨介电常数的材料有望在提高电容器的容量和实现电子元器件的小型化方面有所突破。在此背景下,本文主要采用固相反应合成法成功的制备了元素掺杂的CCTO陶瓷,系统地研究了元素掺杂对CCTO陶瓷的微观结构与电性能的影响,并对其巨介电机制与电学输运行为进行了探讨。本文首先采用固相反应合成法制备了Al掺杂和Li、Al共掺杂的CCTO陶瓷。Al掺杂CCTO陶瓷是利用Al元素置换CCTO中的一部分Cu元素,相当于对CCTO陶瓷进行施主掺杂,研究了Al元素不同掺杂量、以及在特定掺杂量时不同烧结时间CCTO陶瓷的微观结构与介电性能。随着Al元素掺杂含量的增加,CCTO陶瓷的介电常数有了显著的提高。在频率为100Hz时,Al元素掺杂含量为1%时,CCTO的介电常数高达8.7×104,相比未掺杂的CCTO陶瓷,介电常数提高了一倍,并且巨介电常数具有良好的频率稳定性。当Al元素掺杂量达到2%时,其介电常数达到3×105。需要特别指出的是,该陶瓷样品在低频(~105Hz)和高频(~107Hz)分别出现了类徳拜型弛豫色散。同时,随着烧结时间的延长,Al元素掺杂量为1%CCTO陶瓷的介电常数逐渐增加,烧结时间20h的陶瓷介电常数值可达1.03×105。Li、Al元素共同掺杂的CCTO陶瓷,随着掺杂含量的增多,其介电常数逐渐增大,当掺杂含量在5%和10%时,在100Hz频率下,介电常数分别为9.3×104和4.8×105,并伴随着两个类徳拜弛豫色散峰。掺杂导致CCTO陶瓷内部氧空位通过界面极化对介电常数产生贡献,而且随着掺杂量的增多,载流子浓度增加,降低了晶界电阻,致使陶瓷在低频部分介电常数显著提高。掺杂导致了Cu1+/Cu2+与Ti3+/Ti4+离子混价结构的出现,会产生更多的微区极化子增强极化响应,也会提高介电常数。通过紫外光谱的测量,研究了Al元素施主掺杂CCTO陶瓷的禁带间隙变化情况,随着掺杂量的增多,禁带间隙基本呈现逐渐降低的趋势,其禁带间隙由1.92e V降到1.85e V。分析紫外光谱测量结果可知,随着Al掺杂量的增多,陶瓷吸收光波长变长,试验证实了Al掺杂降低了CCTO陶瓷的禁带宽度。Al掺杂CCTO陶瓷直流电导率随着掺杂含量的增多逐渐变大,相应的激活能逐渐降低,进一步证明了Al掺杂提高了陶瓷的载流子浓度,降低了禁带宽度。更多还原

【Abstract】 Giant dielectric constant usually means a material having a high energy density,The high energy density is an important factor,which affect electronic components capacitors, detectors, information storage. So the study of giant dielectric constant of the material is expected to be a breakthrough in improving the capacity of the capacitor and achieve miniaturization of electronic components.In this context, this paper uses solid state reaction method successfully prepared the doping of CCTO ceramics,In the microstructure and properties as well as other aspects of the mechanism for the doping of CCTO ceramics were studied.Firstly, by the method of the solid phase synthesis, Al and Li, Al element commonly doping CCTO ceramics were prepared. Al doping CCTO ceramics using Al element replacement CCTO part of Cu element, which is equivalent to CCTO ceramics donor doping, and researching microstructure and dielectric properties of the different amount and the different sintering time of Al elements doping. With the increase of Al doping content, the dielectric constant of CCTO ceramics have been significantly improved. When Frequency is 100 Hz, Al doping content at 1wt%, CCTO dielectric constant up 8.7 × 104. Compared to undoped ceramic,CCTO dielectric constant doubling and giant dielectric constant have good frequency stability. When Al doping amount to 2wt%, the dielectric constant reaches 3 × 105. It needs to be noted that, Ceramic samples Appeared the Phenomenon of Class Debye relaxation at low frequency(~ 105Hz) and high frequency(~ 107Hz). Meanwhile, with the extension of the sintering time, Al doping amount of 1 wt% CCTO ceramic permittivity gradually increase, when sintering time is 20 h, dielectric constant of Ceramic up 1.03 × 105. CCTO ceramics of Li, Al co-doping, with the increase of doping content, the dielectric constant increases, When the doping content of 5wt% and 10wt%, at 100 Hz frequency, the dielectric constant was 9.3 × 104 and 4.8 × 105, And accompanied by two relaxation dispersion peak.Doping CCTO ceramics lead to internal oxygen vacancies generated contribution to the dielectric constant by interfacial polarization. And with the increase of doping content, the carrier concentration increases, reducing the grain boundary resistance, and resulting in the low frequency portion of the ceramic dielectric constant significantly. Doping leads to Cu1 + / Cu2 + and Ti3 + / Ti4 + ions appear with mixed-valence structure, which will produce more micro Polaron enhanced polarization response and will increase the dielectric constant. By measuring the ultraviolet spectrum, Experiment study the change of the forbidden band gap change of donor doping of Al elements, With the increase in doping, the forbidden band gap basically showing decreasing trend, whose forbidden band gap reduced by the 1.92 e V to 1.85 e V. by analyzing the UV spectrum measurement results, With the increase of Al doping, ceramics absorb ligh t wavelength becomes longer, Al-doped test confirmed CCTO ceramic band gap decreases. with the increase in doping content, dc conductivity of Al-doped CCTO ceramic gradually increases. Corresponding the activation energy decreases. Further evidence of the Al-doped increases the carrier concentration in ceramics, reducing the band gap.更多还原