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Hydroxylclinohumite Mg5(SiO4)2(OH,F)2 is a common monoclinic orthosilicate of the humite group, which, on the one hand, is a prototype of promising materials, and, on the other hand, is an important source of information about both the transport and the presence of water in the Earth's mantle, and therefore studying its thermal behavior is of particular interest. In this paper, the mineral is studied by powder X-ray diffraction for the first time in a wide temperature range (–180 ≤ T ≤ 1000°C). The temperature limits for the existence of the phase are established, the principal values of the thermal expansion tensor are calculated, and a structural interpretation of thermal expansion is given. [ABSTRACT FROM AUTHOR]

In the Na2SO4–K2SO4 system, nine phases are known. In this study, for the first time, the values of the thermal expansion coefficients of continuous high-temperature solid solutions crystallizing in the P63/mmc crystal system, low-temperature limited solid solutions based on natroaphthitalite and aphthitalite (P3-m1), and polymorph II Na2SO4 (Pbnm) in the Na2SO4–K2SO4 system are provided. The genetic succession of polymorphs P3m1 and P3-m1 ↔ P63/mmc, which manifested itself in the double sulfates of this system, is revealed. [ABSTRACT FROM AUTHOR]

The thermal expansion of magnesium borate (Mg3B2O6) is studied by the method of X-ray thermodiffraction in the temperature range 25–1100°C. The coefficients of thermal expansion are calculated as follows: αa = 13.0(5), αb = 8.5(5), αc = 8.0(5), αV = 30(1) × 10–6°С−1 at 25°C; and αa = 20.0(5), αb = 13.0(5), αc = 13.0(5), αV = 46(1) × 10–6°С−1 at 1100°С. The direction of the maximal thermal expansion (αa) is perpendicular to the preferred orientation of the BO3 triangles. [ABSTRACT FROM AUTHOR]

Hydroxylclinohumite Mg5(SiO4)2(OH,F)2 is a common monoclinic orthosilicate of the humite group, which, on the one hand, is a prototype of promising materials, and, on the other hand, is an important source of information about both the transport and the presence of water in the Earth's mantle, and therefore studying its thermal behavior is of particular interest. In this paper, the mineral is studied by powder X-ray diffraction for the first time in a wide temperature range (–180 ≤ T ≤ 1000°C). The temperature limits for the existence of the phase are established, the principal values of the thermal expansion tensor are calculated, and a structural interpretation of thermal expansion is given. [ABSTRACT FROM AUTHOR]