高温高压下二辉橄榄岩的阻抗谱实验研究

 在1.0～4.0 GPa压力、1 073～1 573 K温度和10^-1～10⁷ Hz频率条件下,利用SARLTON-1260阻抗-增益/相位分析仪,就位测定了二辉橄榄岩的阻抗谱。实验结果表明：二辉橄榄岩的阻抗谱对频率具有很强的依赖性,并从阻抗谱的测试原理（颗粒内部、颗粒边缘、样品与电极间的导电机制）上做出了解释;温度是决定二辉橄榄岩电导率的一个重要物理参数,电导率随着温度的升高而增大,lg σ与1/T之间符合Arrenhius关系式;在高压实验中第一次将压力作为测量二辉橄榄岩电导率重要的约束因素,随着压力的增大,电阻率升高、电导率降低。     

高温高压下辉石岩的电导率研究

 利用阻抗谱在1.0~2.0 GPa、温度450~792 K条件下、10⁵~12 Hz的频率范围内,对辉石岩的电导率进行了研究,并且分析了测试频率对电导的影响,结果表明,电导率对频率具有一定的依赖性;在复平面上出现了代表颗粒内部的阻抗弧。辉石岩的激化焓为0.661~0.673 eV,样品中较高的铁含量可能是造成本实验电导率较高的主要原因。     

高温高压下钠长石的阻抗谱实验研究

 在压力为1.0、2.0 GPa和温度为673～973 K条件下,采用交流阻抗谱法在YJ-3000t紧装式六面顶高压设备上原位测量了钠长石的电导率。实验结果表明：在实验的温度和压力范围内,钠长石的电导率在10^-3.0～10^-5.5 S/m变化;钠长石复阻抗的模和相角对频率有很强的依赖性;随着温度T升高,钠长石的电阻率迅速减小,电导率σ增大,并且lg σ与T^-1之间符合Arrhenius关系;在实验压力范围内,随着压力升高,钠长石的电导率降低。采用离子导电机制,对高温高压下钠长石的导电行为进行了合理解释。     

高温高压下黑云斜长片麻岩的电性研究

 在压力1 GPa、温度250~1 100 ℃、频率0.1 Hz~1 MHz的条件下,采用阻抗谱方法,对来自阴山造山带的太古代黑云斜长片麻岩进行了电导率实验研究。实验发现：（1） 所有样品的阻抗谱都是由一个大的高频半圆弧Ⅰ和一个小的被压缩了的低频弧Ⅱ组成,阻抗弧Ⅰ主要代表矿物颗粒内部传导机制,阻抗弧Ⅱ更有可能代表的是样品和电极之间的传导机制;（2） 电导率随温度的变化遵循Arrhenian定律,但在700~750 ℃间有近一个量级的跳跃,通过对比实验前后样品的显微照片和探针分析数据,认为这一电导率的大幅跳跃可能是样品中黑云母发生大量脱水熔融的缘故;（3） 在高温段750~1 100 ℃,部分熔融样品的电导率主要由钠离子传导控制;（4） 在低温段250~700 ℃,样品的激活能为0.53 eV;在高温段750~1 100 ℃,样品的激活能为1.41 eV。激活能的改变可能与样品的结构变化有关,还与样品和熔体中钠的含量以及扩散有关。     

冲击压缩下金属的电导率测量

 探索了一种在兆巴压力冲击压缩下测量金属电导率的新方法——四电极垂向引线法，并用刻槽单晶蓝宝石作绝缘腔体，以消除分流效应对测量结果的影响。用二级轻气炮作为加载手段，测量了铁在终态平衡压力为101～208 GPa压力区间内的电导率（电导率从1.45×10⁶ S/m变化到7.65×10⁵ S/m）。将测量铁电导率的压力范围扩展到了200 GPa以上。实验结果表明，关于金属电导率的Bloch-Grüneisen公式在高达200 GPa冲击压力下仍然有效（对于ε-铁）。     

Co掺杂对YBa_2Cu_3O_(7-δ)电阻率与塞贝克系数的影响

用固态反应法制备了YBa2Cu3-xCoxO7-δ(x=0.0,0.1,0.2,0.5)样品,研究了Co掺杂对YBa2Cu3O7-δ高温区的电阻率和塞贝克系数的影响。随着Co含量的增加,样品的电阻率和塞贝克系数逐渐增大,从金属性导电转变为p型半导体导电。x=0.2和0.5样品的电导活化能在500K处发生突变,高温区的活化能大于低温区的活化能。通过塞贝克系数与温度的关系,计算出x=0.2和0.5样品的费米能级分别为0.02和0.12 eV。当温度高于650-700K时,氧脱附显著影响样品的电输运性质,导致电阻率和塞贝克系数随温度增加而增大。     

水中放电等离子体状态方程的理论研究

 水中放电等离子体通道内温度达2×10⁴～5×10⁴ K、而压力达1～10 GPa。在这样的参数下,等离子体的状态方程已不能用理想气体状态方程来描述。首次考虑了粒子间的相互作用对水中放电等离子体参数下粒子电离能的影响,计算了电子的简并性、带电粒子间的库仑相互作用、原子内部能级扰动所产生的压力。计算结果表明：当H、O原子和离子的总密度n=10²⁹ m^-3时,若考虑电离能漂移,则电子密度提高的最大幅度达70%;电子的简并性对压力的影响很小;粒子间的库仑相互作用在高温区使总压减小较显著,但在所计算的参数范围内,其幅值也不大于10%;当n=10²⁹ m^-3、T≈2×10⁴ K时,原子内部能级的扰动使总压增大约30%。     

钽掺杂二氧化钛薄膜的光电性能研究

采用脉冲激光沉积法 (PLD), 以石英玻璃为衬底制备了钽掺杂TiO₂薄膜并研究了薄膜样品的光电性质. 沉积氧气分气压从0.3 Pa变化到0.7 Pa时薄膜样品的帯隙变化范围是3.26 eV到3.49 eV. 通过测量电阻率随温度的变化关系确定了薄膜内部的主要导电机理. 在150 K到210 K温度范围内, 热激发导电机理是主要的导电机理; 而在10 K到150 K范围内; 电导率随温度的变化复合Mott的多级变程跳跃模型 (VRH); 在210 K到300 K范围内, 电阻率和exp(b/T)^1/2呈正比关系. 关键词： 2')" href="#">Ta掺杂TiO₂ 脉冲激光沉积法 薄膜 导电机理     

高压下单晶橄榄石的电导率

以圣卡洛斯(San Carlos)单晶橄榄石为研究对象,结合交流阻抗谱和金刚石对顶砧(DAC)技术,在300 K、0～19 GPa条件下对其电导率的各向异性进行系统研究。压力标定根据红宝石荧光谱线的漂移以及硅油的拉曼光谱。实验结果表明:在300 K、0～19 GPa条件下,橄榄石[100]方向上的电导率最大,从3.8×10~(-8) S/m增加到9.0×10~(-8)S/m,[010]与[001]方向上的电导率接近,约为[100]方向电导率的1/2～1/3;橄榄石电导率随着压力线性增加,其中[100]方向的电导率随着压力变化的斜率最大。在室温条件下,橄榄石主要的导电机制是小极化子导电,且具有负的活化体积。研究结果表明,在含水量较低的上地幔区域,随着深度增加,压力效应可能导致电导率横向和纵向的不均一性增强。     

甲醇作为压标的拉曼研究

 利用立方氧化锆压腔研究了甲醇在温度301 K、压力169.2~713.8 MPa下C—H伸缩振动ν_{2 835}的拉曼特征,实验结果表明：在试验的压力范围内甲醇稳定,其拉曼位移和压力具有很好的线性关系。加上常压下的数据,拟合后得出压力与甲醇2 835 cm^-1拉曼线频率位移的关系为：p= -3.508 9[(Δν_p)_{2 835}]²+135.17 (Δν_p)_{2 835}+54.397(0.1~713.8 MPa)。因此在实验的压力范围内甲醇作为压标非常合适。     

High–pressure electrical conductivity and Raman spectroscopy of chalcanthite

Abstract

The phase transitions and dehydration of chalcanthite were investigated by electrical conductivity and Raman spectroscopy at 1.0–24.0?GPa and 293–673?K in a diamond anvil cell. At ambient temperature, two secondary phase transitions were observed according to discontinuous changes in the slope of Raman shifts, full width at half maximum and electrical conductivities at ～7.3 and ～10.3?GPa. The dehydration temperatures were determined by the splitting of Raman peaks and changes in electrical conductivity as ～350 and ～500?K at respective ～3.0 and ～6.0?GPa. A positive relationship for chalcanthite between dehydration temperature and pressure is established.     

PbMoO4原位高压拉曼光谱和电导率的研究

 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。     

In-situ control of different oxygen fugacity experimental study on the electrical conductivity of lherzolite at high temperature and high pressure

At pressure 1.0-4.0 GPa and temperature 1073-1423 K and under the control of oxygen fugacity (Mo+MoO₂, Fe+FeO and Ni+NiO), a YJ-3000t multi-anvil solid high-temperature and high-pressure apparatus and Solartron-1260 impedance/Gain-Phase analyzer were employed to analyze the electrical conductivity of lherzolite. The experimental results showed that: (1) within the range of the selected frequencies (10³-10⁶ Hz), either as viewed from the relationship between the real or imaginary part of complex impedance and the frequency, or from the relationship between modulus, phase angle and frequency, it can be seen clearly that the complex impedance has a strong dependence on frequency; (2) with the rise of temperature (T), the electrical conductivity (σ) increased, and Lg σ and 1/T follows the Arrhenius relationship; (3) with the rise of pressure, the electrical conductivity decreased, and activation enthalpy and temperature-independent pre-exponential factor decreased as well. And the activation energy and activation bulk volume of the main charge carrier in the lherzolite have been obtained for the first time, which are 1.68±0.02 eV and 0.04±0.01 cm³/mol, respectively; (4) under the given pressure and temperature, the electrical conductivity tends to increase with increasing oxygen fugacity, and under the given pressure, the activation enthalpy and pre-exponential factor tend to decrease with the rise of oxygen fugacity; (5) at 2.0 GPa and the control of the three solid buffers, Mo+MoO₂, Fe+FeO and Ni+NiO, the exponential factors of electrical conductivity variation range with oxygen fugacity are , and the theoretical model for the relationship between the electrical conductivity of lherzolite and the oxygen fugacity under high pressure has been established for the first time; (6) the electrical conduction mechanism of small polarons provides a reasonable explanation to the variation of conductivity of lherzolite with oxygen fugacity.     

In-Situ High Pressure Raman Spectrum and Electrical Property of PbMoO4

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.     

Experimental measurement of the electrical conductivity of pyroxenite at high temperature and high pressure under different oxygen fugacities

Electrical conductivities of pyroxenite were measured between frequencies of 10^?1 and 10⁶ Hz in a multi-anvil pressure apparatus using different solid buffers (Ni+NiO, Fe+Fe₃O₄, Fe+FeO and Mo+MoO₂) to stabilize the partial pressure of oxygen. The temperature ranged from 1073 to 1423 K (800 to 1200 °C) and the pressure from 1.0 to 4.0 GPa. We observe that: (1) the electrical conductivity (σ) of pyroxenite depends on frequency; (2) σ tends to increase with rising temperature (T), and Log σ and 1/T obey a linear Arrhenius relationship; (3) under control of the buffer Fe+Fe₃O₄, σ tends to decrease with rising pressure, nevertheless the activation enthalpy tends to increase. For the first time we have obtained values for the activation energy and activation bulk volume of the main charge carriers, which are (1.60±0.07) eV and (0.05±0.03) cm³/mol, respectively; (4) for a given pressure and temperature, σ tends to rise with increased oxygen fugacity, whereas the activation enthalpy and preexponential factor tend to decrease; and (5) the behaviour of the electrical conductivity at high temperature and high pressure can be reasonably interpreted by assuming that small polarons provide the dominant conduction mechanism in the pyroxenite samples.     

Electrical conductivity of pulverulent iron-cobalt molybdates Co1−xFexMoO4: evidence for hopping conduction

Different mixed iron-cobalt molybdates Co_1−xFe_xMoO₄ (0 < x ≤ 1) were prepared by means of a ceramic process. The influence of the isostructural substitution of Co²⁺ by Fe²⁺ and Fe³⁺ on the electrical conductivity of CoMoO₄ was studied in the temperature range (50–600°C). The results show that the iron substitution increases the electrical conductivity and changes the conduction mechanism of CoMoO₄. From a band conduction mechanism with an activation energy higher than 0.8 eV the conduction mode transforms into a hopping mechanism between the Fe²⁺ and Fe³⁺ ions in the octahedrally coordinated divalent cation sublattice. The activation energy is lower (0.4 eV) and does not alter around the polymorphic transition temperature. Owing to careful oxidations of the samples into cation deficient phases it was shown that the conductivity is proportional to the [Fe²⁺]/[Fe³⁺] ratio. These mild oxidations confirm the hopping mechanism. The presence of Co²⁺/Co³⁺ pairs has a minor contribution to the overall conductivity process. Paper presented at the 2nd Euroconference, Funchal, Madeira, Portugal, 10 – 16 Sept. 1995