The high-temperature P2/c1–C2/c phase transition in Fe-free Ca-rich P21/c clinopyroxenes
The high-temperature P2/c1–C2/c phase transition in Fe-free Ca-rich P21/c clinopyroxenes
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无铁富钙 P21/c 单斜辉石中的高温 P2/c1–C2/c 相变
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
G. Bromiley
中科院分区：
文献类型：
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作者：
M. Tribaudino;F. Nestola;C. Meneghini;G. Bromiley
使用同步辐射（ESRF，格勒诺布尔），在高达850 °C下，对组成为Ca0.40Mg1.60Si2O6、Ca0.52Mg1.46Al0.05Si1.98O6、Ca0.59Mg1.41Si2O6和Ca0.70Mg1.30Si2O6的无铁单斜辉石进行了原位高温粉末衍射研究。在成分为Ca0.52Mg1.46Al0.05Si1.98O6和Ca0.59Mg1.41Si2O6的样品中，分别在T = 550和300 °C的晶格参数变化中观察到P21/c-C2/c置换相变的证据。成分为Ca0.52Mg1.46Al0.05Si1.98O6的样品的相变行为的朗道模型显示出三临界行为[Tc=547（16）]。与沿着透辉石-顽火辉石连接处具有较低Ca含量的其他样品的转变行为进行比较表明，随着Ca含量的增加，Tc降低，并且从一级转变为三临界行为。在过渡行为的变化有关的反相域在纳米级的相互作用。
An in situ, high-temperature, powder diffraction investigation was performed for iron-free clinopyroxenes with compositions Ca0.40Mg1.60Si2O6, Ca0.52Mg1.46Al0.05Si1.98O6, Ca0.59Mg1.41Si2O6 and Ca0.70Mg1.30Si2O6, up to 850 °C using synchrotron radiation (ESRF, Grenoble). In samples with compositions Ca0.52Mg1.46Al0.05Si1.98O6 and Ca0.59Mg1.41Si2O6, evidence of for the P21/c-C2/c displacive phase transition was seen in changes in lattice parameters at T ≈ 550 and 300 °C respectively. Landau modelling of the phase transition behaviour for the sample with composition Ca0.52Mg1.46Al0.05Si1.98O6 shows a tricritical behaviour [Tc=547(16)]. Comparison with the transition behaviour in other samples with lower Ca contents along the join diopside–enstatite indicates that a decrease in Tc, and a switch from first-order to tricritical behavior occurs with increasing Ca content. The change in the transition behaviour was related to an interaction with the antiphase domains at the nanoscale.