第36卷，第10期 2016年10月
光谱学与光谱分析 Spectroscopy and Spectral Analysis
Vol. 36, No. 10+pp3404-3409
October, 2016
Raman Spectra of Bredigite at High Temperature and HighPressure XIONG Zhi-hua', ZHAO Ming-zhen",HE Jun-guo".4+,LI Yi-peng', LI Hong-zhong.6* 1. School of Earth and Space Science, Peking University, Bejing100871, China
2. School of Material Science and Engineering, South China University of Technology, Guangzhou 510275, China 3. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China
4. Guangdong Provincial Key Lab of Geological Processes and Mineral Resource Survey, Guangzhou510275, China 5. University of Houston, Department of Earth and Atmospheric Sciences, Houston, Texas 77204-5007, USA
6. Key Laboratory of Mineral Resource, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing
100029,China
Abstraet Bredigite was synthesized by using the Piston-Cylinder in 1. 2 GPa and 1 473 K. With external heat ing device and diamond anvil cell, high temperature and high pressure Raman spectra of bredigite were collect ed at temperatures 298, 353, 463, 543, 663, 773 and 873 K and with pressure from 1 atm up to 14. 36 GPs(room temperature). The SEM image showed that the sample consisted of one crystalline phase with grain size ranging from 10 ~ 20 μm. The EPMA data suggest a chemical formula of Car. s(2) Mga s(2, Si. (2, O which was identical to the theoretical component of bredigite. The Raman spectroscopic results indicate there were 29 vi-bration bands of bredigite at high temperature. Some bands were merging, weakening and disappearing in creasingly with the temperature, which was obvious in the range of 800~1 200 cm1. The vibration bands of 909, 927 and 950 cm1 disappeared at 873, 773 and 873 K, respectively. The results primarily indicated that the structure of bredigite was stable under experimental condition. In addition, isobaric mode-Gruneisen pa-rameters and isothermal mode-Gruneisen parameters were calculated, yielding 1. 47(2) and 0. 45(3) as their mean values, respectively. Anharmonic coefficients were estimated based on the high temperature and high pressure Raman experiments, showing that the contributions to anharmonic-effect induced with the SiO vi bration modes were smaller than other modes.
Keywords Bredigite High temperature Raman; High pressure Raman: Anharmonic coefficients
中图分类号：S511
Introduction
文献标识码：A
D0I: 10, 3964/j. issn. 10000593 (2016)10-3404-06
were large polyhedral, M was the octahedron, generally in form of MgO,, and T was the tetrahedron, as SiOt. As to the structure of bredigie, MgO, and SiO, were linked together
Bredigite (Ca, Mg (SiO, ), ) was firstly found in Larne district of Scawt Hill. It was defined as α'-Ca, SiO, which was one of the polymorphic forms of Caz SiO:, but it turned out to be totally different from Ca: SiO, system. The structure of bredigite was a kind of monoclinic one (space group: P2nn). In bredigite, Ca and Mn could be replaced by Ba and Mg to some extent, respectively. The ideal polyhedral formu la of bredigite was X? X5 Y M*[TO,]+ , where X and Y
Received: 2015-07-03; aceepted: 2015-11-29
by sharing the corner O, forming a kind of pinwheel arrange ment (Fig. 1).
bredigite can be formed as follows
Ca, Mg(SiO,)4 : Bredigite
2CazSiO
Calcium orthosilicate
+ Ca Mg(SiO, ):
Merwinite
(1)
As Ca SiO:and Cas Mg(SiO,): were found in both Skarn area and as inclusions in diamond, bredigite was anticipated to be a
Foundation item: National Natural Science Foundation of China(410090371, 41273072, 41303025)
Biography : XIONG Zhi-hua, (1987—), female, a PhD candidate at school of Earth and Space Science, Peking University
方方数据ihuaxiong@pku.edu.cn
* Corresponding authors
e-mail : waynelee01@163. com; lihongzhong01@aliyun. com