钙钛矿过渡金属氧化物的制备和掺杂研究

发布时间：2018-10-31 20:59

【摘要】：自二十世纪五六十年代以来,过渡金属氧化物因其独特的物理特性,引起越来越多人的关注,具备层状钙钛矿结构的过渡金属氧化物更是因其多样的奇异物理特性备受追捧,并且,通过掺杂的方式改变其物性从而更好地满足工业生产需求已成为国内外课题组的研究热点。本文主要通过对高温超导化合物YBa2Cu3O7-δ(YBCO)和自旋轨道耦合化合物Sr_2IrO_4进行制备和掺杂,并研究其结构特性变化,为进一步研究其物性变化提供理论参考依据。采用金属有机物沉积法制备YBCO薄膜,更换不同衬底以及对前驱液按照不掺杂样品中Y3+浓度的十分之一进行Gd3+和Sm3+掺杂,研究衬底对薄膜生长的影响以及掺杂对其结构特性的改变。结果表明YBCO晶粒无法在与之晶格匹配度低的衬底材料之上进行结晶生长;掺杂后YBCO晶体结构产生了轻微的晶格畸变,且掺杂后膜内压应力减弱,导致晶粒c轴取向生长减弱。采用固相反应法制备Sr_2IrO_4化合物,通过Sr缺位掺杂的方式引入空位缺陷,利用正电子湮没技术通过测试样品的寿命谱来研究晶体内部缺陷随掺杂浓度的演变行为,结果表明随着Sr缺位掺杂浓度的增加,正电子的寿命呈现减小的趋势,这是因为当掺杂浓度不断增强时,样品内部产生轻微的晶格畸变导致空位型缺陷体积变小,从而使缺陷的寿命一直变小;当掺杂浓度达到一定程度时,正电子寿命又呈现变大的趋势,这是因为部分空位型缺陷和样品内某些残留的气泡相互作用从而形成了新的复合型缺陷,导致缺陷体积变大,从而使缺陷的寿命变大,同时也导致缺陷浓度降低。这种晶格畸变行为在样品的XRD衍射谱中也有体现,具体表现为各主相峰随着掺杂浓度的增加发生了轻微的偏移。
[Abstract]:Since the 1950s and 1960s, transition metal oxides have attracted more and more attention because of their unique physical properties, and transition metal oxides with layered perovskite structure have been sought after for their various singular physical properties. In addition, changing its physical properties by doping to better meet the needs of industrial production has become a hot research topic at home and abroad. In this paper, the high temperature superconducting compound YBa2Cu3O7- 未 (YBCO) and the spin orbit coupling compound Sr_2IrO_4 are prepared and doped, and their structural characteristics are studied, which provides a theoretical basis for further study of the physical properties of the superconducting compounds. YBCO thin films were prepared by metal-organic deposition method, different substrates were replaced, and the precursor solution was doped with Gd3 and Sm3 according to the concentration of 1/10 Y3 in the undoped samples. The influence of substrate on the growth of thin film and the change of doping on its structure were studied. The results show that YBCO crystal can not grow on the substrate with low lattice matching, and the doped YBCO crystal structure produces slight lattice distortion, and the compressive stress in the film decreases after doping, which leads to the weakening of c-axis orientation growth of the crystal. Sr_2IrO_4 compounds were prepared by solid state reaction, vacancy defects were introduced by Sr vacancy doping, and the evolution of defects with doping concentration was studied by means of positron annihilation technique. The results show that the lifetime of positron decreases with the increase of Sr vacancy doping concentration. So that the life of defects has been reduced; When the doping concentration reaches a certain level, the positron lifetime increases again, which is due to the interaction between some vacancy defects and some residual bubbles in the sample, resulting in the formation of new composite defects, resulting in the defect volume becoming larger. Thus, the defect life is increased and the defect concentration is reduced. The lattice distortion is also reflected in the XRD diffraction spectrum of the sample, which shows that the main phase peaks deviate slightly with the increase of doping concentration.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O611.62

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