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首页> 外文期刊>Physical review >Origin of the crossover between a freezing and a structural transition at low concentration in the relaxor ferroelectric K_(1-x)Li_xTaO_3
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Origin of the crossover between a freezing and a structural transition at low concentration in the relaxor ferroelectric K_(1-x)Li_xTaO_3

机译：弛豫铁电体K_（1-x）Li_xTaO_3中低浓度下的冻结与结构转变之间的转换起点

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摘要

The origin of the relaxor behavior in K_(1-x)Li_xTaO_3 (KLT) and other disordered perovskites is now recognized to be due to the reorientation of the polar nanodomains formed by the correlated dipoles of off-center ions. The collective dynamics of these systems evolve through several temperature stages. On decreasing temperature below the so-called Burns temperature T_B, individual dipoles become correlated within nanosized regions. On further cooling, the slow dynamics of these polar regions allows local lattice distortions to take place and the formation of polar nanodomains at T~* ＜ T_B. At still lower temperature, some relaxors undergo a phase transition while others do not. In KLT, there is a critical Li concentration x_c = 0.022 above which the system undergoes a structural transition at T_c, and below which it freezes in a dipole glass state at T_f. To better understand the nature of this critical concentration, the changes that occur upon crossing it and the nature of the dipole glass state, the collective dynamics of KLT have been studied by dielectric spectroscopy and neutron diffraction for two Li concentrations (x = 0.026 and 0.018), close to but straddling the critical concentration x_c. Two very different transitional behaviors are observed. Just below this critical concentration, KLT displays critical slowing down and the onset of freezing as seen in hydrogen-bonded molecular ferroelectrics, while just above this concentration, KLT undergoes a first-order structural transition.
机译：现在认识到K_（1-x）Li_xTaO_3（KLT）和其他无序钙钛矿中弛豫行为的起源是由于偏心离子的相关偶极子所形成的极性纳米域的重新取向。这些系统的集体动力学通过几个温度阶段演变。在将温度降低到所谓的“烧伤温度” T_B以下时，各个偶极子在纳米区域内变得相关。在进一步冷却时，这些极性区域的缓慢动力学使局部晶格发生变形，并在T〜* ＜T_B处形成极性纳米域。在更低的温度下，一些弛豫器会发生相变，而另一些则不会。在KLT中，存在一个临界的Li浓度x_c = 0.022，高于该浓度时，系统在T_c处发生结构转变，而低于该温度时，系统在T_f处以偶极玻璃态冻结。为了更好地了解此临界浓度的性质，越过临界浓度所发生的变化以及偶极玻璃态的性质，已通过介电谱和中子衍射研究了两个Li浓度（x = 0.026和0.018）的KLT集体动力学。 ），但接近临界浓度x_c。观察到两个非常不同的过渡行为。正如在氢键分子铁电中所看到的那样，恰好在该临界浓度以下，KLT表现出临界的减速和冻结的开始，而在此浓度之上，KLT经历了一级结构转变。

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  • 来源
    《Physical review》 |2015年第13期|134106.1-134106.8|共8页
  • 作者

    Ling Cai; Jean Toulouse; Leland Harriger; R. Gregory Downing; L. A. Boatner;

  • 作者单位

    Physics Department, Lehigh University, Bethlehem, Pennsylvania 18015, USA ,Science and Technology Division, Coming Inc., Corning, New York 14831, USA;

    Physics Department, Lehigh University, Bethlehem, Pennsylvania 18015, USA;

    NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA;

    NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA;

    Center for Radiation Detection Materials and Systems, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

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  • 正文语种 eng
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  • 关键词

    dielectric loss and relaxation; neutron scattering;

    机译：介电损耗和松弛;中子散射;

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