High-Temperature, High-Pressure X-ray Investigation of Dicalcium Silicate |
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Authors: | Corinne Remy Denis Andrault Michel Madon |
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Affiliation: | Département des Géomatériaux CNRS-URA 734, Institut de Physique du Globe de Paris, 75252 Paris Cedex 05, France;Laboratoire de Physique et Mécanique des Géomatériaux CNRS-URA 734, Universitéde Marne-la-Vallée, 93166 Noisy le Grand Cedex, France |
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Abstract: | Energy-dispersive X-ray powder diffraction experiments have been investigated at high temperature and room pressure, and at high pressure and room temperature, starting from either γ- or β-Ca2SiO4. High-temperature studies were performed up to 1980 K, using a versatile heating cell. The high-temperature phase transformations previously described were reexamined. Volume and linear thermal expansions were measured for each Ca2SiO4 polymorph, γ, β, α';L,α';H, and α. Volume thermal expansion increases with increasing temperature except for α';H, whose thermal expansion tends to decrease at elevated temperature. High-pressure investigations were performed in the 0–15 GPa pressure range, using a diamond anvil cell, with silicon oil as the pressure-transmitting medium. The value of the room-pressure bulk modulus K0 , assuming a second-order BirchMurnaghan equation of state with K'0= 4, is 140(8) GPa for γ-Ca2SiO4. The γ olivine form exhibits anisotropic compression, with the c axis as the most compressible. From such in situ high-pressure X-ray investigations, the γ-→Ca2SiO4 phase transformation induced by cold compression is clearly evidenced and extends from 2 to about 5 GPa. |
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