CaCu₃Ti₄O₁₂基巨介电陶瓷的制备与介电性能研究

【作者】 熊利蓉；

【导师】 杨祖培；

【作者基本信息】 陕西师范大学 ， 材料学， 2010， 硕士

【摘要】 CaCu3Ti4O12 (CCTO)是一种介电常数εr高达104并且具有很好的温度稳定性的巨介电材料,已成为近几年学术界关注的焦点之一。然而,CCTO具有较高的介电损耗(tanδ-0.1),严重地影响了它的应用。本文以CaCu3Ti4012陶瓷为研究对象,通过研究不同的制备方法(固相合成法、NaCl熔盐法、CaCl2熔盐法和半化学法)、不同工艺条件、A位取代、B位变化对CaCu3Ti4O12陶瓷相结构、显微结构与介电性能的影响规律,以获得高介电常数和低介电损耗的高介电材料。研究的主要内容如下：首先,采用传统固相法制备CCTO陶瓷,系统地研究了不同工艺条件对CaCu3Ti4O12陶瓷相结构、显微结构、介电性能的影响。结果表明：当预烧温度为900℃,烧结温度为1070-1110℃时,陶瓷样品获得了纯的类钙钛矿结构,且晶界清晰、气孔较少、致密性好、晶粒尺寸较大、晶粒饱满、平均晶粒尺寸在100μm左右。此时,当测试频率为1 kHz时,陶瓷具有最佳的介电性能,其介电常数高达6.14×104,介电损耗为0.044；当测试频率为40 Hz-105Hz范围内,陶瓷均能获得巨介电常数,其介电常数都在6.0×104以上,介电损耗值都小于0.48。其次,系统研究了固相法、NaCl熔盐法、CaCl2熔盐法和半化学法对CaCu3Ti4O12陶瓷显微结构、介电常数及介电损耗的影响。结果表明：固相法制备的CCTO陶瓷具有更大的晶粒,更清晰的晶界,晶粒排列紧密,致密性良好。在40-105Hz频率范围内,固相法、NaCl熔盐法、半化学法制备CCTO陶瓷的介电常数都在104以上,尤其是固相法制备的CCTO陶瓷的介电常数高达6.0×104以上,而CaCl2熔盐法制备的CCTO陶瓷的介电常数最高值只有1.5×104。在-50-55℃温度范围内,10 kHz频率下,固相法制备的CCTO陶瓷的介电常数高达3.1×104,且它的介电损耗低于0.04,同时还具有良好的温度稳定性；而NaCl熔盐法、半化学法、CaCl2熔盐法制备的CCTO陶瓷的介电损耗分别高达至0.12、0.13、0.39。这表明了固相法制备CCTO陶瓷具有高的介电常数和低的介电损耗。再次,系统地研究了Ti3+的含量对CCTO陶瓷相结构、显微结构、介电性能及阻抗谱的影响。结果表明：当x<4.00时,CaCu3TixO12出现了第二相(Cu2O)；当x≥4.00时,获得了纯相。根据SEM和EDX分析的结果发现,当x<4.00时,陶瓷晶界区域存在大量的富铜相(Cu2O)。随着Ti含量的增加,陶瓷晶界区域的铜变得越来越少,晶界变得越来越薄。当x=4.00时,形成具有晶界清晰且致密的CCTO陶瓷。阻抗谱分析发现,随着Ti含量的增加,陶瓷的晶粒电阻Rg和晶界电阻Rgb先减小后增加的趋势,当x=4.00时,Rg和Rgb最小。室温介电频谱发现,在40 Hz-105Hz频率范围内陶瓷(x=4.00)的介电常数都在5.50×104以上；在1kHz下陶瓷的介电性能为：εr=6.15x104,tanδ=0.044。最后,系统地研究了Sr含量对Ca1-xSrxCu3Ti4O12陶瓷显微结构、介电常数及介电损耗的影响。当x=0.10时,CSCTO陶瓷的晶粒尺寸达最大值。随着Sr含量的增加,CSCTO陶瓷的室温介电常数先增加后降低。当x=0.10时,在40 Hz-4.0×105 Hz频率范围内,CSCTO陶瓷具有高的介电常数和较低的介电损耗；在1 kHz下陶瓷的介电常数和介电损耗分别为71153、0.022；在1 kHz下,在-50℃-100℃温度范围内CSCTO (x=0.10)陶瓷的介电常数大于65000,介电损耗低于0.05。同时,还系统地研究和比较了碱土金属(Mg、Ba、Sr)取代对Ca0.9A0.1Cu3Ti4O12陶瓷显微结构、介电常数及介电损耗的影响。研究表明,在40 Hz-105kHz频率范围内,Ca0.9Sr0.1Cu3Ti4O12陶瓷比Ca0.9Mg0.1Cu3Ti4O12、Ca0.9Ba0.1Cu3Ti4O12、CaCu3Ti4O12陶瓷具有更大的晶粒、更薄的晶界、更高的介电常数以及低的介电损耗。综上所述,利用固相法在预烧温度为900℃,烧结温度为1100℃条件下制备出了具有优良电性能的Ca0.9Sr0.1Cu3Ti4O12陶瓷。Ca0.9Sr0.1Cu3Ti4O12陶瓷具有最佳的介电性能。1 kHz下,比纯CCTO陶瓷相比较,其陶瓷的介电性能常数从6.15×104增加到7.12×104,介电损耗从0.044降低到0.022,达到降低陶瓷介电损耗的目的,为进一步研究降低CCTO陶瓷的介电损耗奠定了基础。更多还原

【Abstract】 CaCu3Ti4O12 (CCTO) is dielectric material with high dielectric constantεr of about 104, and good temperature stability, as in recent years the academic focus of attention. On the other hand, CCTO ceramics with a high dielectric loss (tanδ-0.1) affects its application.In this paper, the phase structure, microstructure and dielectric properties of CaCu3Ti4O12 ceramics were studied through different preparation methods (solid-phase synthesis method, molten salt method and semi-chemical method), different conditions, and then further study on this basis the B variant, A-substituted on CaCu3Ti4O12 ceramic to accommodate the high dielectric constant and lower dielectric loss.Firstly, systematically the affect of under different conditions on dielectric properties of CaCu3Ti4O12 ceramics was studied. The results show that precalcined at 900℃, sintering temperature of 1070℃-1110℃sintering of the ceramics has good dielectric properties. When the calcining temperature is 900℃, the ceramics obtain a pure perovskite the structure, clearly grain boundary, lesser porosity, higher density and larger grain size, plump grain. the average grain size are about 100μm. At 1 kHz at room temperature, the preheat temperature of 900℃ceramic has the best dielectric properties, the dielectric constant of about 6.14×104, the dielectric loss of 0.044. Room temperature in the 40 Hz-105 Hz frequency range,1070℃-1110℃sintering temperature range of sintered ceramic can be huge dielectric constant, the dielectric constant are more than 6.0 x 104, the dielectric loss values is less than 0.48.Secondly, the microstructure, dielectric constant and dielectric loss effects of the CaCu3Ti4O12 ceramics by prepared the system of the solid phase, NaCl molten salt method, CaCl2 molten salt method and the semi-chemical method was studied. The results showed that the CCTO ceramics by prepared solid-phase has greater grain, more clearly the grain boundary, Closely arranged grains, good density. In the 40-105 Hz frequency range, the dielectric constant of CCTO ceramics of by prepared solid state, NaCl molten salt method, semi-chemical synthesis are more than 104, especially the dielectric constant of the CCTO ceramics prepared by solid-phase is up to 6.0×104 more, the highest dielectric constant of CCTO ceramics by prepared CaCl2 molten salt is only 1.5×104. At-50-55℃temperature range, the frequency of 10 kHz, dielectric constant of CCTO ceramics prepared by the the solid phase is up to 3.1×104, its dielectric loss is less than 0.04, and it also has good temperature stability. However, the dielectric loss of CCTO ceramics by prepared the NaCl flux method, semi-chemical method, CaCl2 molten salt is up to 0.12,0.13,0.39, respectively. This shows that CCTO ceramics prepared by solid phase has high dielectric constants and low dielectric loss.Thirdly, the effect of Ti content on the phase structure, microstructure and dielectric properties of CaCu3TixO12 ceramics was discussed. The X-ray diffraction patterns showed that there was a second phase (Cu2O) when x<4.00, and a pure phase was obtained when x≥4.00. SEM and EDX analysis showed that a large number of copper-rich phase (Cu2O) was found at the grain boundary region of ceramics with x<4.00. Impedance spectroscopy analysis showed that, with the Ti content increasing, the grain resistance Rg and the grain boundary resistance Rgb decrease at first, minimum values(1.48 Q.cm and 94.5 kΩ.cm, respectively) were obtained at x=4.00, and then increased. From room temperature dielectric frequency spectrum, it was found that the dielectric constant of the ceramics with x=4.00 are more than 5.50×104 in the frequency range of 40 Hz to 105 Hz, and at 1 kHz, dielectric constant value is as follows:εr=6.15×104 tanδ=0.044.Lastly, the effects of Sr content on the phase structure, microstructure and dielectric properties of CSCTO ceramics were discussed. A pure structure without any impurity phases can be confirmed by the X-ray diffraction patterns. Scanning electron microscopy analysis illuminate that the grains of CSCTO (x=0.10) ceramics are greater than that of CCTO. And then the grains of CSCTO (x>0.10) ceramics gradually decrease as x increasing. It is found that the CSCTO (x= 0.10) ceramics have the higher permittivity (71153) and the lower dielectric loss (0.022) at 1 kHz at room temperature. In the range of-50-100℃, the dielectric constant of the CSCTO (x=0.10) is no less than 65000 and the dielectric loss is no more than 0.05 at 1 kHz. The results indicate that the CSCTO (x=0.10) display lower dielectric loss and good temperature stability. The current-voltage nonlinear behavior of CSCTO ceramics is also investigated. The effects of alkaline earth metals (Mg, Ba, Sr) substituted on the microstructure, dielectric constant and dielectric loss of Ca0.9A0.1Cu3Ti4O12 ceramics were discussed. The results showed that the grain of Ca0.9Sr0.1Cu3Ti4O12 ceramics is bigger and the grain boundary of it is thinner than that of Ca0.9Mg0.1Cu3Ti4O12, Ca0.9Ba0.1Cu3Ti4O12, CaCu3Ti4O12 ceramics. Room temperature in the frequency range of 40 Hz-105 kHz, the dielectric constant of Ca0.9Sr0.1Cu3Ti4O12 ceramics is higher than that of pure CCTO ceramics, Ca0.9Mg0.1Cu3Ti4O12 and Ca0.9Ba0.1Cu3Ti4O12, ceramics. The dielectric loss of Ca0.9Sr0.1Cu3Ti4O12. ceramics is lower than than of pure CCTO ceramics.更多还原