Electrical Transport Properties Of Zn Mn₂O₄ Under High Pressure

As a candidate of new lithium-ion battery anode materials, because of its high energy density, good cycle stability, abundant resources, environmental friendliness, ZnMn₂O₄ has caused a great deal of research interest. In this thesis, we select ZnMn₂O₄ as the research object. By using high pressure in situ AC impedance spectroscopy experiments, DC resistivity experiments, SEM and TEM, we have studied systematically the electronic transport properties under high pressure, and the effect of crystal microstructure on the electrical properties. The results of study are as follows.First, the electronic transport properties of ZnMn₂O₄ under high pressure were studied. By high pressure in situ AC impedance spectroscopy experiments, we found that at pressures below 20.6 GPa, the resistance of the sample decreases at a slower rate with pressure increasing, but from 20.6 GPa to 27.5 GPa, the resistance decreases at a faster rate with pressure increasing. We attributed the abnormal change at 20.6 GPa of the electronic transport properties to structure phase transition. By high pressure in situ DC resistivity experiments, we found that the resistivity of the sample also decreases with pressure increasing, but resistivity increase appears at 20.6 GPa, which could also be attributed to structure phase transition. With further compression up to 28.1 GPa, we find that discontinuous change of resistivity has taken place in the sample. Below 28.1 GPa, resistivity decreases rapidly with pressure increasing, but above 28.1 GPa, resistivity decreases slowly with pressure increasing.Second, to explore the reasons for abnormal changes of electrical properties at 28.1 GPa, samples under different pressures were characterized by TEM. We found that grain refinement took place between 26 GPa to 30 GPa. Therefore, we determine that the abnormal change of electrical transport properties at about 28 GPa is caused by the grain refinement.Third, in addition to the systematic study of ZnMn₂O₄, in the thesis, we also have improved high pressure high temperature（HPHT） experimental device, and designed internally cooled diamond anvil cell. Union of circulating water cooling technology and diamond anvil cell technology, we can build experimental apparatus and method under extreme conditions of in situ HPHT measurements for a variety of physical quantities. Internally cooled diamond anvil cell could be able to provide samples with high temperature environment, while the cell itself can be maintained at room temperature. The cell can be used for electrical, optical, magnetic, thermal, mechanical, acoustic and other tests under HPHT.