系列稀土钯合金中111 In/Cd溶质原子的核四极相互作用
Nuclear quadrupole interactions of 111In/Cd solute atoms in a series of rare-earth palladium alloys
摘要：
使用γ射线扰动角相关（PAC）技术，在具有L12结构的稀土钯相RPd 3中测量了111 In/Cd探针原子的核四极相互作用。对具有RPd 3相场的贫Pd和富Pd边界的组成的成对样品进行测量，典型地为75和78原子%警局在大多数相位中检测到两个信号，对应于立方R-和非立方Pd-子晶格上的探针原子。的R-和Pd-亚晶格上的探针的位点分数的父在探针原子的网站偏好的特点。对于所有富含Pd的样品，探针专门占据R-亚晶格，与溶质原子倾向于占据元素的亚晶格的启发式规则一致，其中存在缺陷。对于贫Pd合金，R= Tb，Er，Yb，Lu，Y和Sc，探针只占据Pd亚晶格。对于Pd贫合金与R= Ce，Pr，Nd，Sm和Eu，探针占据两个亚晶格，与现场分数作为温度的函数而变化。相比之下，探针只占据的R-亚晶格中的Pd贫LaPd 3。从波动的电场梯度引起的核弛豫确定子Cd探针的Pd-亚晶格上的跳跃频率。从温度依赖性的扩散跳跃的活化能谱，并发现线性增加的晶格参数沿系列Pr，Nd，Eu和Sm的减少。据信，CePd 3中的跳跃频率甚至比PrPd 3中的跳跃频率更高，但在Tb、Er、Yb、Lu、Y和Sc钯化物中太低而无法检测到。网站的偏好和跳转频率之间的相关性进行了说明和讨论。本文提供了一个完整的帐户的测量的跳跃频率的镉探针原子和比较与其他系列的L12相类似的测量。
英文摘要：
Nuclear quadrupole interactions were measured at 111In/Cd probe atoms in rare-earth palladium phases RPd3 having the L12 structure using the technique of perturbed angular correlation of gamma rays (PAC). Measurements were made for pairs of samples having compositions of the Pd-poorer and Pd-rich boundaries of the RPd3 phase fields, typically 75 and 78 at.% Pd. Two signals were detected in most phases, corresponding to probe atoms on cubic R- and non-cubic Pd-sublattices. Site preferences of parent In-probe atoms were characterized by site-fractions of probes on the R- and Pd-sublattices. For all Pd-rich samples, probes exclusively occupied the R-sublattice, consistent with a heuristic rule that solute atoms tend to occupy the sublattice of an element in which there is a deficiency. For Pd-poorer alloys with R= Tb, Er, Yb, Lu, Y and Sc, probes exclusively occupied the Pd-sublattice. For Pd-poorer alloys with R= Ce, Pr, Nd, Sm and Eu, probes occupied both sublattices, with site fractions varying as a function of temperature. In contrast, probes only occupied the R-sublattice in Pd-poorer LaPd3. Jump frequencies on the Pd-sublattice of daughter Cd-probes were determined from nuclear relaxation caused by fluctuating electric field gradients. Activation enthalpies for diffusional jumps were determined from temperature dependences and found to increase linearly as the lattice parameter decreases along the series Pr, Nd, Eu and Sm. Jump frequencies are believed to have been even higher in CePd3 than in PrPd3, but were too low to be detectable in Tb, Er, Yb, Lu, Y and Sc palladides. A correlation between site preferences and jump frequencies is noted and discussed. This paper provides a complete account of measurements of jump frequencies of Cd-probe atoms and comparisons with similar measurements made on other series of L12 phases.
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