Experimental Study on the Effect of Pressure on the Electrical Conductivity of Pure and Iron Sulfide-Bearing Olivine
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摘要: 在YJ-3000 t紧装式六面顶大腔体压机上，用Solartron-1260阻抗/增益-相位分析仪，在1～3 GPa、723～1273 K的条件下，原位测量了纯的和含15%(质量分数)FeS的橄榄石电导率。实验结果表明：在实验温度范围内，含15% FeS的橄榄石电导率比纯橄榄石的电导率高2～3个数量级，且电导率值在0.1～10 S/m范围内；纯的和含15% FeS的橄榄石电导率都随着温度的增加而增大，但是纯的橄榄石电导率对温度的敏感性更强；纯的和含15% FeS的橄榄石电导率随压力变化表现出相反的特性，随着压力的升高，纯橄榄石电导率微弱地降低，而含15% FeS的橄榄石电导率显著地增加。由含15% FeS的橄榄石电导率对温度、压力的效应以及实验获得的活化焓可知，15% FeS在橄榄石中形成了相互连通的网络，主导着橄榄石的导电过程。Abstract: We performed in situ electrical conductivity measurements on pure and iron FeS-bearing olivine in a multi–anvil apparatus using the impedance spectroscopy technique under the condition of 1–3 GPa and 723–1273 K. The experimental results indicated that the electrical conductivities of 15% (mass fraction) FeS–bearing olivine, in the range of 0.1–10 S/m, are 2 to 3 orders of magnitude higher than that of pure olivine in the experimental temperature range. The electrical conductivities of pure and 15% FeS-bearing olivine increase with increasing temperature. The dependence of the electrical conductivity of pure olivine on temperature is much stronger. The effect of pressure on the electrical conductivity of pure and iron FeS-bearing olivine is different. With the rise of pressure, the electrical conductivity of pure olivine slightly decreases, whereas the electrical conductivity of the 15% FeS-bearing olivine increases significantly. Based on the experimental results including the Arrhenius parameters, it is proposed that the 15% FeS can form an interconnected network in olivine, which dominates the conduction process of olivine.
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Key words:
- olivine /
- FeS /
- pressure /
- electrical conductivity
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图 2 (a)纯橄榄石和(b)含15% FeS的橄榄石的背散射图
Figure 2. Backscattered electron images of (a) pure olivine and (b)15% FeS–bearing olivine
图 3 不同温度压力条件下纯橄榄石和含15% FeS的橄榄石复阻抗谱的对比
Figure 3. Comparison of complex impedance spectra of pure olivine and 15% FeS–bearing olivine under different temperature and pressure conditions
图 4 纯的和含15% FeS橄榄石的电导率对数与温度倒数的关系
Figure 4. Logarithm of electrical conductivity reciprocal temperature for pure olivine and 15% FeS–bearing olivine at different pressures
表 1 样品电导率的Arrhenius关系拟合参数
Table 1. Fitted parameters of Arrhenius relation for the electrical conductivity of samples
Sample p/GPa T/K lg $\sigma_0 $ $\sigma_0 $/(S∙m−1) ${\Delta H}/{\rm{eV}}$ ${\gamma^2}$ 1 723–1273 2.53 338.84 1.18 0.9913 Olivine 2 723–1273 1.96 91.20 1.11 0.9781 3 723–1273 1.05 11.22 1.03 0.9867 1 723–1273 0.47 2.95 0.20 0.9953 FeS-bearing olivine 2 723–1173 1.73 53.70 0.29 0.9802 3 723–1073 2.78 602.56 0.39 0.9845 Note: ${\gamma}^2 $—adjust R-square. 
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