High-temperature behavior of lamprophyllite and barytolamprophyllite

Zhitova E. S., Panikorovskii T. L., Yakovenchuk V. N., Krzhizhanovskaya M. G.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 3. P. 82-94

https://doi.org/10.30695/zrmo/2018.1473.06

Full text is available on eLIBRARY.RU

Language: Russian

Abstract

According to the high-temperature X-ray powder diffraction data, lamprophyllite and barytolamprophylhte are stable up to 925 and 850 °C, respectively. The temperature of decomposition was defined for barytolamprophyllite by DSC and TGA methods as 897 °C. Analysis of the X-ray diffraction pattern during the heating has not detected any significant changes, implying the absence of phase transitions. Behavior of lamprophyllite and barytolamprophylhte at high-temperature is strongly anisotropic, thermal expansion coefficients (×10⁶) along crystallographic axes at T = 200 °C are as following: aa = 12.6(6), ab = 7.7(1), ac = 4.4(2) °C^–1 for lamprophyllite, and a_a = 11.8(5), a_b = 5.7(1), a_c = 3.4(3) °C^–1 for barytolamprophylhte. At T = 600 °C these values are a_a = 15.2(5), a_b = 7.7(1), a_c = 2.2(2) °C^–1 for lamprophyllite, and a_a = 12.3(7), a_b = 5.7(1), a_c = –3.8(4) °C^–1 for barytolamprophylhte. The contraction along the axis ñ was observed for barytolamprophyllite, but did not for lamprophyllite; it is caused by thermal oxidation of iron.

Key words: lamprophyllite, barytolamprophylhte, high-temperature X-ray diffraction.