Equation of state and phase transition in KAlSi3O8 hollandite at high pressure
Equation of state and phase transition in KAlSi3O8 hollandite at high pressure
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DOI：
10.2138/am.2006.1879
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发表时间：
2006-02
影响因子：
3.1
通讯作者：
T. Ferroir;Tsuyoshi Onozawa;T. Yagi;S. Merkel;N. Miyajima;N. Nishiyama;T. Irifune;T. Kikegawa
中科院分区：
文献类型：
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作者：
T. Ferroir;Tsuyoshi Onozawa;T. Yagi;S. Merkel;N. Miyajima;N. Nishiyama;T. Irifune;T. Kikegawa
本文用高压原位X射线衍射技术研究了室温下压力高达32 GPa的四硅镁矾结构（KAlSi_3O_8镁矾）。在20 GPa左右，发生了由tetraSiO_4/m相向新相的相变。这种转变在压力释放时是可逆的，没有明显的滞后，因此这种新的高压相对于环境条件是不可淬灭的。与过渡相关联的体积变化被发现是小的（不可测量的），这表明二阶过渡。高压相的衍射花样可以在单斜晶胞（空间群I2/m）中被索引，其与BaMn_8 O_（16）Hollandite等结构。单斜晶胞的γ角在过渡区以上连续增加。Birch-Murnaghan状态方程与KAlSi 3 O 8-Hollandite的压力-体积数据拟合得到体积模量K 0 = 201.4（7）GPa，K '0 = 4.0。
Abstract The tetragonal hollandite structure (KAlSi3O8 hollandite) has been studied up to 32 GPa at room temperature using high-pressure in-situ X-ray diffraction techniques. A phase transformation from tetragonal I4/m phase to a new phase was found to occur at about 20 GPa. This transition is reversible on release of pressure without noticeable hysteresis and hence this new high-pressure phase is unquenchable to ambient conditions. The volume change associated with the transition is found to be small (not measurable), suggesting a second order transition. The diffraction pattern of the highpressure phase can be indexed in a monoclinic unit cell (space group I2/m), which is isostructual with BaMn8O16 hollandite. The γ angle of the monoclinic unit cell increases continuously above the transition. A Birch-Murnaghan equation of state fit to pressure-volume data obtained for KAlSi3O8 hollandite yields a bulk modulus K0 = 201.4 (7) GPa with K’0 = 4.0.