蓝柱石的高温X射线衍射、差热-热重分析、偏振红外光谱和高压拉曼光谱研究

High Temperature X-ray Diffraction,DSC-TGA,Polarized FTIR and High Pressure Raman Spectroscopy Studies on Euclase

通过高温X射线衍射(XRD)、差热-热重分析、偏振红外光谱和高压拉曼光谱研究了江西大余的蓝柱石的热膨胀行为、稳定性、羟基峰在(010)面上的强度变化及其常温高压拉曼光谱特征。结果表明,蓝柱石在1273K完全非晶化,其热膨胀系数αV为1.2(1)×10-5+0.16(1)T×10-9/K。蓝柱石在750K开始发生分解反应,最大的反应速率发生在1266K。在蓝柱石的(010)面上,羟基吸收峰在光的偏振方向与c轴夹角为70°和250°时最强,在光的偏振方向与c轴夹角为160°和340°时最弱。在常压至12.3GPa的压力范围内,蓝柱石没有发生相变。通过高压拉曼光谱计算得到了蓝柱石的mode Grüneisen参数的算术平均值为0.52(2)、thermal Grüneisen参数为0.64(2)。另外,根据Grüneisen关系式可以求得thermal Grüneisen参数,其值为0.70(6)。

Euclase samples collected from Jiangxi,China,were studied using high temperature X-ray diffraction,DSC-TGA analysis,polarized FTIR and high pressure Raman.High temperature X-ray diffraction data suggested that euclase becomes fully amorphous at ～1273 K （ambient pressure）,and its volumetric thermal expansion coefficient is αV=1.2（1） × 10^-5＋ 0.16（1）T× 10^-9/K （temperature range of 298-1223 K）.The DSC-TGA data suggested that euclase starts to break down at 750 K and reaches the maximum reaction rate at 1266 K.The polarized FTIR data collected in the （010） plane of euclase indicated that the absorbance of OH^- is strongest when the angle between the IR polarizer and c-axis of euclase is 70°or 250° and is weakest when 160° or 340° which suggested that the orientation of the OH dipole parallels to the former direction.High pressure Raman data collected with a diamond-anvil cell at room temperature suggested no phase transition occurs as pressure increasing up to 12.3 GPa.Based on the high pressure Raman data,the calculated average mode Grüneisen parameter and thermal Grüneisen parameter of euclase are 0.52（2） and 0.64（2）,respectively.Alternatively,the calculated thermal Grüneisen parameter from Grüneisen equation for euclase is 0.70（6）.