论文部分内容阅读
采用固相反应法制备了La0.67Ca0.33Mn0.9A0.1O3(其中A为Cr、Co、Fe、Al、Cu)系列Mn位替代的氧化物样品;利用正电子湮没对该系列样品的结构缺陷进行了分析,结果表明:τ1的变化范围不大,表明样品主要受大尺寸点缺陷的影响,τ2的变化比较明显,说明样品内存在一定数量的空洞及微空洞等缺陷.类比合金中正电子长寿命与缺陷簇之间的关系,估算了元素替代后样品的缺陷半径大小,可能大的空位团簇、位错和晶界在样品中起着重要作用.按Cr、Co、Fe、Al、Cu的掺杂顺序,平均寿命τavg逐渐增加,而电子密度ne则逐渐减小.说明元素掺杂引起锰离子局域环境的改变,样品中的铁磁与反铁磁作用的相互竞争及样品内部电子局域化所形成的极化行为等因素的影响,导致了正电子寿命各参数的变化.
The samples of La0.67Ca0.33Mn0.9A0.1O3 (where A is Cr, Co, Fe, Al, Cu) Mn series were prepared by the solid-state reaction method. The positron annihilation The results show that the range of τ1 is not large, which indicates that the sample is mainly affected by large size point defects and the change of τ2 is obvious, which indicates that there are a certain number of cavities and micro-cavities in the sample. The relationship between lifetime and defect clusters was evaluated, and the defect radius of sample after element substitution was estimated.The possible vacancies, dislocations and grain boundaries play an important role in the samples.According to Cr, Co, Fe, Al, Cu Doping order, the average life expectancy τ avg gradually increased, while the electron density ne is gradually reduced. This shows that element doping lead to local changes in the manganese ion environment, the sample of ferromagnetic and antiferromagnetic interactions with each other and sample internal electronic Localization of the polarization caused by the formation of other factors, led to positron lifetime parameters of the changes.