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硼在高压下具有复杂的结构和多样的物理性质,对其结构和性质的深入研究具有很重要的意义,一直引起理论和实验研究领域的关注。高压下进行电学性质测量是获得物质物理性质的有效手段,利用集成在金刚石对顶砧上的微电路,在高压下和两个不同温度范围内对β相硼进行了电导率测量,分析了导电机制随压力的变化规律。在0~28.1 GPa范围内,β相硼的电导率随着压力的增大是逐渐增大的,卸压后样品的电导率不能回到最初的状态,是一个不可逆的变化过程;由室温到423 K的范围内,β硼的电导率随着温度的不断增加有明显的上升趋势,并且随着压力的升高,电导率变化逐渐加快。此外,对样品在14.5 GPa和18.6 GPa压力下,用溅射到金刚石对顶砧上的氧化铝薄膜做绝热层,对样品进行了激光加热实验,最高温度达到2 224 K,电导率随着温度的上升而增大,结果显示,β相硼的电学特征仍然属于半导体的特征范围内。 相似文献
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Phase Transition Behavior of LiCr 0.35 Mn0.65O2 under High Pressure by Electrical Conductivity Measurement 下载免费PDF全文
The electrical conductivity of powdered LiCr 0.35 Mn0.65O2 is measured under high pressure up to 26.22 GPa in the temperature range 300-413 K by using a diamond anvil cell. It is found that both conductivity and activation enthalpy change discontinuously at 5.36 GPa and 21.66 GPa. In the pressure range 1.10-5.36 GPa, pressure increases the activation enthalpy and reduces the carrier scattering, which finally leads to the conductivity increase. In the pressure ranges 6.32-21.66 GPa and 22.60-26.22 GPa, the activation enthalpy decreases with pressure increasing, which has a positive contribution to electrical conductivity increase. Two pressure-induced structural phase transitions are found by in-situ x-ray diffraction under high pressure, which results in the discontinuous changes of conductivity and activation enthalpy. 相似文献
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The charge transport behavior of strontium fluoride nanocrystals has been investigated by in situ impedance measurement up to 35 GPa.It was found that the parameters changed discontinuously at each phase transition.The charge carriers in SrF_2 nanocrystals include both F~-ions and electrons.In the Fm3 m phase,pressure makes the electronic transport easier,while makes it more difficult in the Pnma phase.The defects at grain boundaries dominate the electronic transport process.Pressure could make the charge-discharge processes in the Fm3 m phase much easier,but make it more difficult in the Pnma phase. 相似文献
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We report on the intriguing electrical transport properties of compressed CaF_2 nanocrystals. The diffusion coefficient,grain and grain boundary resistances vary abnormally at about 14.37 GPa and 20.91 GPa, corresponding to the beginning and completion of the Fm3m-Pnma structural transition. Electron conduction and ion conduction coexist in the transport process and the electron conduction is dominant. The electron transference number of the Fm3m and Pnma phases increases with pressure increasing. As the pressure rises, the F~- ion diffusion and electronic transport processes in the Fm3m and Pnma phases become more difficult. Defects at grains play a dominant role in the electronic transport process. 相似文献
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In-situ high pressure Raman spectra and electrical conductivity measurements of scheelite-structure compound PbMoO4 are presented. The Raman spectrum of PbMoO4 is determined up to 26.5 GPa on a powdered sample in a diamond anvil cell (DAC) under nonhydrostatic conditions. The PbMoO4 gradully experiences the trans- formation from the crystal to amorphous between 9.2 and 12.5 GPa. The crystal to amorphous transition may be due to the mechanical deformation and the crystalographic transformation. Furthermore, the electrical conductivity of PbMoO4 is in situ measured accurately using a microcircuit fabricated on a DAC based on the van der Pauw method. The results show that the electrical conductivity of PbMoO4 increases with increases of pressure and temperature. At 26.5 GPa, the electrical conductivity value of PbMoO4 at 295K is 1.93 - 10-4 S/cm, while it raises by one order of magnitude at 430K and reached 3.33 - 10-3 S/cm. However, at 430K, compared with the electrical conductivity value of PbMoO4 at 26.5 GPa, it drops by about two order magnitude at 7.4 GPa and achieves 2.81 × 10^-5 S/cm. This indicates that the effect of pressure on the electrical conductivity of PbMoO4 is more obvious than that of temperature. 相似文献
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利用传统的四电极方法在金刚石对顶砧(DAC)上进行原位的样品电导率测量时,如果金属垫片样品孔内壁不能完全绝缘,测量结果将会存在很大的误差.为避免该实验误差的产生,作者提出了用双电极模型进行电导率测量的方法,即在DAC砧面上制备一个圆形测量电极的同时,将金属垫片样品孔的内壁做为第二个测量电极,并利用有限差分方法对电导率进行计算.通过这种方式,由金属垫片不绝缘而产生很大测量误差的问题得以解决.实验结果表明测量相对误差被控制在7%以下. 相似文献
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钼酸铅(PbMoO4)具有高的声光品质因数、低的声损耗、良好的声阻抗匹配等性质,被广泛应用于声光偏转器、调制器、可调滤光器、声表面波器件等各类声光器件,其优异的低温闪烁性能亦引起人们的注意,具有在核设备方面的应用潜力。为探讨其晶体结构和物理性质,在金刚石对顶砧上原位测量了PbMoO4的拉曼光谱,并测量了其在几个不同压力点下电导率随温度的变化。实验发现,压力在12.5 GPa时,拉曼峰完全消失,说明压力在10.8~12.5 GPa之间PbMoO4样品出现了非晶态转变。当从26.5 GPa卸压到9.4 GPa时,PbMoO4的拉曼谱在低波数出现无序化,而在2.4 GPa压力下858 cm-1峰又重新出现,说明样品结构由无序向晶化回复。压力在10.8 GPa以上时,电导率随着温度的增加而显著增加,且随着压力的增加也明显增加。 相似文献
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