Thermodynamic behaviour of the high-temperature \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P\bar 1{\text{-}}I\bar 1$$\end{document} phase transition along the CaAl2Si2O8–SrAl2Si2O8 join

被引:0
作者
M. Tribaudino
P. Benna
F. Nestola
C. Meneghini
E. Bruno
机构
[1] Università di Parma,Dipartimento di Scienze della Terra
[2] Università di Torino,Dipartimento di Scienze Mineralogiche e Petrologiche
[3] CNR,Istituto di Geoscienze e Georisorse
[4] Sezione di Torino,Bayerisches Geoinstitut
[5] Universität Bayreuth,Dipartimento di Fisica “E. Amaldi”
[6] Università di Roma 3,undefined
关键词
phase transition; Ca–Sr feldspars; Powder diffraction; Synchrotron radiation; Solid solution;
D O I
10.1007/s00269-005-0469-4
中图分类号
学科分类号
摘要
In situ high-temperature synchrotron radiation powder diffraction patterns were taken from room temperature to T = 740°C from synthetic feldspars along the join CaAl2Si2O8–SrAl2Si2O8 (An–SrF). Three samples of composition An95SrF5, An90SrF10 and An85SrF15 were investigated, and the evolution of cell parameters with T was determined by Rietveld analysis of powder X-ray diffraction patterns. The high-temperature \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P\bar 1{\text{-}}I\bar 1$$\end{document} phase transition, previously observed with Tc = 241°C in anorthite, was found in An95SrF5, An90SrF10 and An85SrF15 feldspars at Tc = 233(5)°, 195(2)° and 174(2)°C respectively. The transition was revealed by the disappearance of critical reflections and variations in the rate of change of cell parameters with temperature. A significant, although small (between 0.0025 and 0.0012 at room temperature), spontaneous strain could be measured, allowing the thermodynamic behaviour of the transition to be modelled. A second-order trend for An90SrF10 and An85SrF15 [β = 0.504(7) and 0.505(7) respectively] or nearly second-order for An95SrF5[β = 0.458(4)] was observed in contrast with tricritical behaviour of end member anorthite. An extrapolation of the Tc versus composition to room temperature indicates that the critical composition for the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P\bar 1$$\end{document} phase is An60SrF40.
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页码:314 / 321
页数:7
相关论文
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