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Experimental verification of the ab initio phase transition sequence in SrZrO3 and comparisons with SrHfO3 and SrSnO3 (实验验证从头算的SrZrO3相变序列及其与SrHfO3和SrSnO3的比较)
发布时间:2017-02-20

Experimental verification of the ab initio phase transition sequence in SrZrO3 and comparisons with SrHfO3 and SrSnO3 (实验验证从头算的SrZrO3相变序列及其与SrHfO3SrSnO3的比较) 
Ashok Kumar, Shalini Kumari, Hitesh Borkar, Ram S Katiyar & James Floyd Scott
npj Computational Materials
 3, Article number: 2 (2017)
doi:10.1038/s41524-016-0002-y
Published online:19 January 2017
Abstract| Full Text | PDF OPEN

摘要:本研究报道了对SrZrO3SZO)所作Raman研究的细致结果,SZO Raman光谱有三个异常特点:1)在ω频率处有小的跳动区,2)有强度消失区,3)有一个温度导数dω(T)/dT急剧变化,该区从低于T = 600 K的单调区,到高于600 KCurie–Weiss依赖区,一直外推到已知相变温度T = 970 K时的零频率区,从而证明急剧变化具有移位性。此外,预测的高应力下P4mm铁电相从极化-电压实验获得了初步支持。在600 - 650 K范围内的新相推断结果与中子研究不符。本研究还对SZO与其家族成员SrSnO3SrHfO3作了比较,并讨论了Kennedy Knight所得结论的不同之处。我们发现,SrHfO3的一个已知相变也是带有通用模式的移位。 

Abstract: We present detailed Raman studies of SrZrO3 (SZO) that show three anomalies in Raman modes: One has a small jump in frequency ω, one has its intensity vanish, and a third has a sharp change in temperature derivative dω(T)/dT from flat below T = 600 K to a Curie–Weiss dependence above 600 K with extrapolation to zero frequency at the known transition temperature T = 970 K, thereby proving the latter to be displacive. In addition, the P4mm ferroelectric phase predicted at high stresses has preliminary support from polarization-voltage experiments. The inference of a new transition in the temperature region 600–650 K is in disagreement with neutron studies. Comparisons are given for family member SrSnO3 and SrHfO3, and we discuss the different conclusions of Kennedy and Knight. We show that a known transition in SrHfO3 is also displacive with a well-behaved soft mode. 

Editorial Summary

Dielectrics: into a new phase 绝缘体:研究进入新阶段

由印度、英国和美国的研究人员共同确定了一种具有意外原子排列结构的材料,有望应用于电子器件。来自CSIR国家物理实验室的Ashok Kumar及其同事观察到锆酸锶在650 K的相变。锆酸锶是电绝缘体,因其有较大的介电常数而在半导体技术领域有很大应用潜力。它具有钙钛矿结构,受热后其原子结构在不同的温度发生相应的改变。但相变所带来的效应仍是一个争论的问题。Kumar及其同事通过测定与原子振动相关的拉曼光谱和介电光谱,研究了锆酸锶的结构。从光谱结果中他们确定了锆酸锶的三个异常特征,并由此推断了一个新相变的存在。 

An unexpected atomic arrangement in a material useful for electronics is identified by researchers in India, the UK, and the USA. Ashok Kumar from the CSIR-National Physical Laboratory and co-workers observe a phase change in strontium zirconate at 650 K. Strontium zirconate is an electrical insulator that has great potential in the semiconductor-technology because of its large dielectric constant. As this so-called perovskite is heated, its atomic structure changes at specific temperatures. But the sequence of these phase changes is still a matter of debate. Kumar and colleagues study the structure of strontium zirconate by measuring the optical emission associated with atomic vibrations—a method known as Raman spectroscopy and dielectric spectroscopy. They identify three anomalous features in these results that infer the presence of a new phase transition. 

 
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