三氧化二镓的高压拉曼光谱研究

β-Ga2O3是一种宽禁带半导体材料(Eg=4.8 eV).研究β-Ga2O3在高压(高应力)条件下的相稳定性和晶格动力学特性对其材料应用具有重要的参考价值.目前关于Ga2O3在高压下的晶格动力学特性研究较少,且Ga2O3的β→α的高压相变压力仍然具有争议.本工作采用基于金刚石压砧(DAC)的高压拉曼光谱技术研究了Ga...     

Raman scattering from highly-stressed anvil diamond

The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell(DAC) experiments. Here we point out that the high-frequency edge of the diamond Raman phonon corresponds to the Brillouin zone(BZ) center Γ point as a function of pressure. The diamond Raman pressure gauge relies on the stability of crystal lattice of diamond under high stress. Upon the diamond anvil occurs failure under the uniaxial stress(197 GPa), the loss of intensity of the first-order Raman phonon and a stressdependent broad Raman band centered at 600 cm^-1 are observed, which is associated with a strain-induced local mode corresponding to the BZ edge phonon of the L1 transverse acoustic phonon branch.     

Evidence for a High-Pressure Isostructural Transition in Nitrogen

We observed an isostructural phase transition in the solid nitrogen λ-N₂ at approximately 50 GPa accompanied by anomalies in lattice parameters, atomic volume and Raman vibron modes. The anomalies are ascribed to a slight reorientation of the nitrogen molecules, which does not seem to affect the monoclinic symmetry(space group p2_1/c). Our ab initio calculations further confirm the phenomena, and suggest an optimized structure for the λ-N₂ phase. In addition, a ne...     

High-pressure Raman study of osmium and rhenium up to 200 GPa and pressure dependent elastic shear modulus C44

High-pressure Raman scattering from hexagonal close-packed (HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C₄₄ has been deduced from the Raman-active mode E_2g, which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works, a further study indicates that the $C_{44}^\prime/C_{44}$ ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.     

固态离子晶体β-K0.294Ga1.969O3的高压与变温拉曼光谱研究

β-镓酸盐（β-gallate）型化合物是一种非常有应用前景的固态离子导体,在储能领域具有重要的应用价值。该类型化合物导电层中往往可以容纳过量的碱金属离子,使得该体系体现出复杂的晶格动力学行为,这也为进一步理解其导电机制带来了困难。压力与温度两个参量均可以通过改变原子间的间距而影响材料的结构,在研究材料的动力学过程,尤其在研究离子的扩散过程方面有很大的应用价值。迄今为止,对于温度依赖的β-镓酸盐型化合物的特性研究很少,且尚无β-镓酸盐型结构化合物的高压研究。由于激光拉曼散射技术在研究物质晶格动力学方面的独特优势,尤其压力与温度依赖的拉曼光谱可以提供重要的结构信息,是研究物质晶格动力学行为的有效实验手段。使用大腔体静高压技术成功合成了一种新型的β-镓酸盐型K_0.294Ga_1.969O₃(KGO)晶体,利用扫描电镜、能谱对晶体进行了表征,通过单晶X射线衍射对其晶体结构进行了解析,并与β-Ga₂O₃的晶体结构进行了对比分析。利用高压和变温拉曼光谱研究了KGO导电层中无序碱金属离子的晶格动力学行为。研究发现,由尖晶石层与疏松的离子导电层交替排列而成的β-镓酸盐型KGO晶体结构在压力23.3 GPa条件下仍可保持稳定;由于振动模式不同,高频拉曼模与低频拉曼模的压力系数存在着显著差异,并表现出显著的对压力诱导非谐性。在约300 ℃,KGO中K+发生热激活,表现在与碱金属K+运动相关的低频拉曼模的强度迅速增加,而与Ga-O多面体相关的高频振动模强度增加缓慢,与此同时,K+在沿着导电平面的方向上发生了无序扩散过程。研究结果将有助于深入地理解β-镓酸盐型结构化合物的导电机制,而且对于实现β-镓酸盐型化合物精确的计算控制和掺杂尤为重要。