Original paper

Phase transitions and thermal expansion of BaCO3 and SrCO3 up to 1413 K

Nie, Shufang; Liu, Yang; Liu, Qiong; Wang, Meili; Wang, Hejin

European Journal of Mineralogy Volume 29 Number 3 (2017), p. 433 - 443

published: Jun 1, 2017

DOI: 10.1127/ejm/2017/0029-2612

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Abstract

The phase evolution and thermal expansivity of synthetic orthorhombic BaCO3 (α-BaCO3) and SrCO3 (α-SrCO3) were studied up to 1413 K using high-temperature powder X-ray diffraction. The α-BaCO3 phase transformed into a trigonal β phase at 1073-1093 K with an increase in molar volume by 2.7%, and further to a cubic γ phase at 1233-1253 K with 0.2% increase in molar volume. The α-SrCO3 phase transformed into a trigonal β phase at ~1173 K. The fitted parameters for volume thermal expansion coefficients (α V (T) = a 0(10-5 K-1) + a 1 (10-8 K-2)T) are a 0 = 4.0(4), a 1 = 4.0(6) for α-SrCO3; a 0 = 4.4(5), a 1 = 3.9(7) for α-BaCO3; a 0 = 6.5(2) and a 0 = 6.8(1) for the β and γ phase of BaCO3, respectively. The β-BaCO3 phase exhibits negative expansion along the a axis, which may help to design new materials with tunable thermal behavior when it is mixed with materials with positive thermal expansion. The aragonite-group carbonates (CaCO3, SrCO3, and BaCO3) have similar bulk thermal expansivity, but their anisotropy and linear expansivities vary with the size of the cation.

Keywords

thermal expansionhigh temperaturecarbonatesphase transitionx-ray diffractionsrco3baco3