摘要
为研究钛酸铜钙的电子结构及变化对介电性能的影响规律,采用第一性原理密度泛函理论计算钛酸铜钙陶瓷的电子结构与光学介电函数,通过溶胶-凝胶法制备稀土铕掺杂改性的钛酸铜钙陶瓷。系统研究掺杂不同量铕对陶瓷晶体结构、微观形貌特征以及介电性能的影响。结果表明钛酸铜钙中Cu-O和Ti-O之间存在强烈的共价键,形成CuO_(4)正方形结构和TiO 6八面体结构。CuO_(4)正方形结构决定钛酸铜钙的价带,TiO 6八面体结构决定其导带。钛酸铜钙的静态介电常数为5.30,并在光子能量为2.45 eV处达到最大峰值。钛酸铜钙的能量损失峰在10 eV附近,与等离子体振荡有关。X射线衍射分析表明所有样品均为体心立方结构,扫描电镜分析表明铕的掺杂能够抑制陶瓷晶粒长大,并使晶粒均匀化。室温频谱表明掺杂后样品介电常数有所降低,但仍为巨介电陶瓷,同时介电损耗在104~105 Hz处达到最小值0.0014;介电温谱表明铕掺杂能够提高陶瓷的温度稳定性并降低损耗,在75~200℃下的损耗均低于0.05。结合第一性原理计算与实验数据发现,铕掺杂使得价带顶的峰值更加扩展,带隙增大,陶瓷的绝缘性增强,介电损耗变小,介电性能优化。
In order to study the influence of the electronic structure and its changes on the dielectric properties of copper calcium titanate,the electronic structure and optical dielectric function of copper titanate calcium ceramics were calculated by using the first principle based on density functional theory,and the ceramics were synthesized by the sol-gel method.The effects of different amounts of Eu 3+on the crystal structure,morphology and dielectric properties of ceramics were systematically investigated.Strong covalent bond exists between Cu-O and Ti-O in copper titanate calcium,thereby forming CuO_(4)square structure and TiO 6 octahedron structure.CuO_(4)square structure determines the valence band of copper titanate calcium,while TiO 6 octahedron structure determines its conduction band.The static dielectric constant of copper titanate calcium is 5.30,and its maximum peak value is reached at the photon energy of 2.45 eV.The peak of energy loss is around 10 eV and is related to plasma oscillation.X-Ray diffraction results confirmed that as-synthesized samples are all single phase with center cubic structure.The microstructure shows that Eu 3+doped can inhibit the growth of ceramic grains and homogenize grains.Compared with copper titanate calcium,the values of dielectric constant(103~104)is slightly decreasing and the dielectric losses of minimum value is as low as 0.0014 of the doped samples in the range from 104 Hz to 105 Hz at the room temperature.The doped samples could enhance the dielectric temperature stability and reduce the dielectric losses below 0.05 in the temperature range from 75℃to 200℃.First-principles calculations and the experimental data indicate that Eu 3+doping could extended the peak of top of valence band,induce to increase the band gap and enhance the insulation of ceramics.Finally,the reduction in the dielectric loss is achieved as well as optimization of the dieleclric performace.
作者
马翠英
杜慧玲
刘佳
杜娴
冉宏培
MA Cuiying;DU Huiling;LIU Jia;DU Xian;RAN Hongpei(College of Materials Science and Engineering,Xi’an University of Science and Technology,Xi’an 710054,China)
出处
《西安科技大学学报》
CAS
北大核心
2021年第4期724-730,共7页
Journal of Xi’an University of Science and Technology
基金
国家自然科学基金项目(51372197)
陕西省自然科学基础研究计划(2019JQ-806)
陕西省教育厅科学研究计划(19JK0525)。
关键词
钛酸铜钙
第一性原理
溶胶-凝胶法
介电性能
copper titanate calcium
first-principles
sol-gel method
dielectric properties
