Experimental determination of thermal expansivity of calcium ferrite-type MgAl2O4 and its application to thermodynamical assessment of thermoelastic parameters
Hiroshi Kojitani, Mei Gonai, Yoshiyuki Inaguma, Masaki Akaogi
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引用次数: 0
Abstract
High-temperature X-ray diffraction measurements of calcium ferrite (CF)-type MgAl2O4 were performed in a temperature range of 300–673 K at atmospheric pressure. From temperature dependence of the unit cell volume, thermal expansivity (α) was determined to be α(T) = (2.46 ± 0.13) × 10–5 + (1.2 ± 0.3) × 10–8T in 1/K. Thermoelastic parameters of isothermal bulk modulus at zero pressure (KT0), its pressure derivative (KT′) and temperature derivative [(∂KT0/∂T)P] of MgAl2O4 CF were optimized by iteration calculation combining the least squares fitting of a third-order Birch–Murnaghan equation of state to previous P–V–T data with α calculation using the Grüneisen relation equation, α = γthCV/(KT0V) where γth and CV are thermal Grüneisen parameter and isochoric heat capacity, respectively. γth was constrained by the α measured in this study. When pressure data were rescaled by Au equations of state which are different from that adopted in the previous study and temperature data were corrected using pressure dependence of electromotive force of a W–Re thermocouple, KT0, KT′ and (∂KT0/∂T)P were assessed to be 216(4) GPa, 3.9(3) and − 0.027(3) GPa/K, respectively. It was suggested that the optimized α was about 17% lower than that determined by the previous study at 2000 K.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)