Thermal Expansion and Polymorphism of Slawsonite SrAl2Si2O8

Abstract

Slawsonite’s (SrAl2Si2O8) structure evolutions depending on temperature (27–1000 ℃) have been studied by in situ single-crystal X-ray diffraction. The SrO7 polyhedron expands regularly with the temperature increase. Silicon and aluminum cations are ordered in tetrahedral sites of the studied slawsonite; no significant changes in their distribution as temperature increases were observed. Slawsonite demonstrates a relatively high volume thermal expansion (αV = 23 × 10–6 °C–1) with high anisotropy, typical for framework feldspar-related minerals and synthetic compounds. It was found that, contrary to previously published data, the crystal structure of slawsonite is stable in the studied temperature range and no phase transitions occur up to 1000 °C. The role of Ca and Ba substitution for Sr and Al/Si ordering on polymorphism of natural MAl2Si2O8 (M = Ca, Sr, Ba) is herein discussed.

Thermal behaviour of filatovite – a rare aluminoarsenate mineral of the feldspar group

“…A hemisphere of diffraction data (with a frame width of 0.5°) was collected. After that this crystal was mounted on a quartz fibre placed in a quartz capillary and fixed between the fibre and the capillary wall (see Gorelova et al ., 2021, for more details) to obtain SCXRD data under high-temperature conditions. High-temperature diffraction data were collected at 200, 400, 600 and 800°C.…”

Synthesis, Growth, and Luminescence Properties of Rare Earth Borates KSrY(BO3)2: Tb3+ and Tb4+

“…The single crystal of KSrTb­(BO 3 ) 2 was studied under heating in air in situ by single crystal X-ray diffraction (SCXRD) using a four-circle XtaLAB Synergy-S diffractometer, operated with monochromated Mo Kα radiation (λ­[Mo Kα] = 0.71073 Å) at 50 kV and 1 mA and equipped with an HyPix-6000HE detector with a high-temperature FMB Oxford system. For these experiments, the single crystal with an approximate size of 0.02 × 0.05 × 0.07 mm 3 was mounted on the quartz glass fiber, which was placed into the quartz capillary 0.3 mm in outer diameter and 0.01 mm of wall thickness, produced by Hampton Research (see ref for more details). The diffraction data were collected under heating at 27, 500, and 600 °C and at 27 °C after cooling.…”