6H型六方钙钛矿相BaGeO_(3)的高温高压合成  

Synthesis of 6H-Type Hexagonal Perovskite Phase of BaGeO_(3) at High Temperature and High Pressure

作　　者：谢亚飞 姜昌国 罗兴丽 谭大勇[1,2,3] 肖万生 XIE Yafei;JIANG Changguo;LUO Xingli;TAN Dayong;XIAO Wansheng(CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou 510640,Guangdong,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]广东省矿物物理与材料研究开发重点实验室,广东广州510640 [3]中国科学院深地科学卓越创新中心,广东广州510640 [4]中国科学院大学,北京100049

出　　处：《高压物理学报》2021年第5期12-19,共8页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(41572030,41372047);中国科学院战略性先导科技专项(B类)(XDB18010403)。

摘　　要：利用金刚石对顶砧高压装置,结合显微激光双面加热技术,对BaGeO_(3)开展了高温高压实验研究。常温常压下赝硅灰石相的BaGeO_(3)于12 GPa左右开始非晶化。进一步加压到22 GPa并对已完全非晶化的BaGeO_(3)样品进行(1800±200)K的高温处理,拉曼光谱显示其转变成一种未见报道的高压新相。在0~17.4 GPa压力范围对BaGeO_(3)高压新相开展同步辐射X射线衍射测试,其衍射谱可以用6H型六方钙钛矿相进行指标化,并且卸压到常压时仍保持稳定。以6H型钙钛矿相为结构模型,分别对17.4 GPa和常压下的X射线衍射谱进行Rietveld结构精修,获得其结构参数。应用二阶Birch-Murnaghan状态方程拟合实验体积-压力数据,得到其体弹模量K0=150(2)GPa和零压晶胞体积V0=373.0(3)Å3。在实验研究的基础上,对6H型钙钛矿相BaGeO_(3)进行第一性原理理论计算,所得不同压力下的晶格常数和体积数据与实验结果符合得很好,状态方程参数K0=153(1)GPa,V0=374.2(1)Å3。20.0 GPa时计算的拉曼光谱也很好地描述了拉曼实验测量结果。研究结果补充了赝硅灰石相BaGeO_(3)在更高温压条件下的结构相转变。6H型钙钛矿相BaGeO_(3)的获得为进一步表征该相的物理化学性质奠定了基础,为开发高性能钙钛矿结构锗酸盐材料提供了可能性,同时对于理解硅酸盐钙钛矿结构的相变规律及稳定性、地球下地幔物理化学性质及其变化等具有重要的指示意义。Barium germanate(BaGeO_(3))was studied using double-sided laser-heating diamond anvil cell(LHDAC).At ambient conditions,BaGeO_(3) has a pseudowollastonite structure.At about 12 GPa,BaGeO_(3) crystal begin to translate into an amorphous phase.The amorphous BaGeO_(3) was further pressurized to about 22 GPa and then heated at(1800±200)K conditions.Raman spectra shows the amorphous BaGeO_(3) transforms into a new high pressure phase,which has not been reported so far.The new high pressure phase of BaGeO_(3) was further measured with the synchrotron radiation X-ray diffraction in the pressure ranges of 0−17.4 GPa.The diffraction patterns can be indexed with a 6H-type hexagonal perovskite structure and this structure remained stable as the pressure unloading to ambient pressure.In order to obtain the structural parameters of the new high pressure phase of BaGeO_(3),the X-ray diffraction patterns of 17.4 GPa and ambient pressure were refined with a model structure of 6H-type perovskite using the Rietveld method.The experimental pressure-volume data was fitted with the second-order Birch-Murnaghan equation of state,and obtained the volume bulk modulus and zero-pressure unit-cell volume are K0=150(2)GPa and V0=373.0(3)A3 respectively.On the basis of the experimental results in this study,we also carried out the first-principle theoretical calculation on the 6H-type perovskite BaGeO_(3).The calculated lattice constants and volume with the corresponding pressures are good agreement with the experimental results.Furthermore,the calculated volume bulk modulus and zero-pressure unit-cell volume are K0=153(1)GPa,V0=374.2(1)A3 respectively.The calculated Raman spectra at 20.0 GPa is also well consistent with the experimental results.This study not only complements the structural phase transition of pseudowallastonite BaGeO_(3) at high temperature and high pressure,but also builds a solid foundation for further characterizing the physical and chemical properties of pseudowallastonite BaGeO_(3),and gives a chance to develop the

关 键 词：BaGeO3 6H型六方钙钛矿相 RIETVELD结构精修 拉曼光谱 高温高压 

分 类 号：O521.2[理学—高压高温物理] P311.9[理学—物理]