McKnight Ruth E A, Howard C J, Carpenter M A
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
J Phys Condens Matter. 2009 Jan 7;21(1):015901. doi: 10.1088/0953-8984/21/1/015901. Epub 2008 Dec 1.
Elastic behaviour associated with the hierarchy of tilting transitions in SrZrO(3) has been examined using resonant ultrasound spectroscopy on a ceramic sample at temperatures between 153 and 1531 K. Changes in slope of the evolution of resonance frequencies with temperature indicate that phase transitions occur at 1038 K ([Formula: see text]), 1122 K ([Formula: see text]), and 1367 K ([Formula: see text]). Strain analysis of previously recorded neutron diffraction data shows that the [Formula: see text] and [Formula: see text] transitions are close to tricritical in character, and that [Formula: see text] is first order. Deviations from the form of the elastic behaviour predicted by Landau theory are found. In particular, elastic softening in the vicinity of the [Formula: see text] transition suggests that local dynamical fluctuations between individual tilt systems occur, rather than a discontinuous switch from one phase to another. Determinations of the mechanical quality factor, Q, show that SrZrO(3) in the [Formula: see text] phase is a classically high-Q (i.e. non-dissipating) cubic material. I4/mcm and Imma phases both have much greater dissipation (low Q), which is tentatively attributed to the mobility of twin walls. The room temperature Pnma phase is unexpectedly much stiffer than both I4/mcm and Imma phases and has high Q. It appears that when two separate tilt systems operate, as in Pnma, they can interact to reduce strain/order parameter relaxations.
利用共振超声光谱法，在153至1531K的温度范围内，对陶瓷样品SrZrO(3)中与倾斜转变层次相关的弹性行为进行了研究。共振频率随温度变化的斜率变化表明，在1038K（[公式：见原文]）、1122K（[公式：见原文]）和1367K（[公式：见原文]）发生了相变。对先前记录的中子衍射数据进行应变分析表明，[公式：见原文]和[公式：见原文]转变在性质上接近三临界点，而[公式：见原文]是一级相变。发现了与朗道理论预测的弹性行为形式的偏差。特别是，在[公式：见原文]转变附近的弹性软化表明，单个倾斜系统之间发生了局部动态波动，而不是从一个相到另一个相的不连续转变。机械品质因数Q的测定表明，处于[公式：见原文]相的SrZrO(3)是一种典型的高Q（即无耗散）立方材料。I4/mcm相和Imma相都有更大的耗散（低Q），这初步归因于孪晶界的迁移率。室温下的Pnma相比I4/mcm相和Imma相都意外地硬得多，且具有高Q。似乎当两个独立的倾斜系统运行时，如在Pnma相中，它们可以相互作用以减少应变/序参量弛豫。
