Interface and scale effects are the two most important factors which strongly affect the structure and the properties of nano-/micro-crystals under pressure.We conduct an experiment under high pressure in situ alterna...Interface and scale effects are the two most important factors which strongly affect the structure and the properties of nano-/micro-crystals under pressure.We conduct an experiment under high pressure in situ alternating current impedance to elucidate the effects of interface on the structure and electrical transport behavior of two Zn Se samples with different sizes obtained by physical grinding.The results show that（i） two different-sized Zn Se samples undergo the same phase transitions from zinc blend to cinnabar-type phase and then to rock salt phase;（ii） the structural transition pressure of the859-nm Zn Se sample is higher than that of the sample of 478 nm,which indicates the strong scale effect.The pressure induced boundary resistance change is obtained by fitting the impedance spectrum,which shows that the boundary conduction dominates the electrical transport behavior of Zn Se in the whole experimental pressure range.By comparing the impedance spectra of two different-sized Zn Se samples at high pressure,we find that the resistance of the 478-nm Zn Se sample is lower than that of the 859-nm sample,which illustrates that the sample with smaller particle size has more defects which are due to physical grinding.展开更多
Electrical transport properties of bismuth vanadate(BiVO4) are studied under high pressures with electrochemical impedance spectroscopy. A pressure-induced ionic-electronic transition is found in BiVO4. Below 3.0 GPa,...Electrical transport properties of bismuth vanadate(BiVO4) are studied under high pressures with electrochemical impedance spectroscopy. A pressure-induced ionic-electronic transition is found in BiVO4. Below 3.0 GPa, BiVO4 has ionic conduction behavior. The ionic resistance decreases under high pressures due to the increasing migration rate of O2-ions. Above 3.0 GPa the channels for ion migration are closed. Transport mechanism changes from the ionic to the electronic behavior. First-principles calculations show that bandgap width narrows under high pressures, causing the continuous decrease of electrical resistance of BiVO4.展开更多
The electrical transport properties and structures of Y2 O3/ZrO2 solid solution have been studied under high pressure up to 23.2 GPa by means of in situ impedance spectroscopy and x-ray diffraction(XRD) measurements.I...The electrical transport properties and structures of Y2 O3/ZrO2 solid solution have been studied under high pressure up to 23.2 GPa by means of in situ impedance spectroscopy and x-ray diffraction(XRD) measurements.In the impedance spectra, it can be found that the pressure-dependent resistance of Y2 O3/ZrO2 presents two different change trends before and after 13.3 GPa, but the crystal symmetry still remains stable in the cubic structure revealed by the XRD measurement and Rietveld refinement.The pressure dependence of the lattice constant and unit cell volume shows that the Y2 O3/ZrO2 solid solution undergoes an isostructural phase transition at 13.1 GPa, which is responsible for the abnormal change in resistance.By fitting the volume data with the Birch–Murnaghan equation of state, we found that the bulk modulus B0 of the Y2 O3/ZrO2 solid solution increases by 131.9% from 125.2 GPa to 290.3 GPa due to the pressure-induced isostructural phase transition.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404133 and 11374121)the Program of Science and Technology Development Plan of Jilin Province,China(Grant No.20140520105JH)
文摘Interface and scale effects are the two most important factors which strongly affect the structure and the properties of nano-/micro-crystals under pressure.We conduct an experiment under high pressure in situ alternating current impedance to elucidate the effects of interface on the structure and electrical transport behavior of two Zn Se samples with different sizes obtained by physical grinding.The results show that（i） two different-sized Zn Se samples undergo the same phase transitions from zinc blend to cinnabar-type phase and then to rock salt phase;（ii） the structural transition pressure of the859-nm Zn Se sample is higher than that of the sample of 478 nm,which indicates the strong scale effect.The pressure induced boundary resistance change is obtained by fitting the impedance spectrum,which shows that the boundary conduction dominates the electrical transport behavior of Zn Se in the whole experimental pressure range.By comparing the impedance spectra of two different-sized Zn Se samples at high pressure,we find that the resistance of the 478-nm Zn Se sample is lower than that of the 859-nm sample,which illustrates that the sample with smaller particle size has more defects which are due to physical grinding.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11774126,11774174 and 11404133
文摘Electrical transport properties of bismuth vanadate(BiVO4) are studied under high pressures with electrochemical impedance spectroscopy. A pressure-induced ionic-electronic transition is found in BiVO4. Below 3.0 GPa, BiVO4 has ionic conduction behavior. The ionic resistance decreases under high pressures due to the increasing migration rate of O2-ions. Above 3.0 GPa the channels for ion migration are closed. Transport mechanism changes from the ionic to the electronic behavior. First-principles calculations show that bandgap width narrows under high pressures, causing the continuous decrease of electrical resistance of BiVO4.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFA0305900)the National Natural Science Foundation of China(Grant Nos.11774126,11774174,1674404,and 51772125)
文摘The electrical transport properties and structures of Y2 O3/ZrO2 solid solution have been studied under high pressure up to 23.2 GPa by means of in situ impedance spectroscopy and x-ray diffraction(XRD) measurements.In the impedance spectra, it can be found that the pressure-dependent resistance of Y2 O3/ZrO2 presents two different change trends before and after 13.3 GPa, but the crystal symmetry still remains stable in the cubic structure revealed by the XRD measurement and Rietveld refinement.The pressure dependence of the lattice constant and unit cell volume shows that the Y2 O3/ZrO2 solid solution undergoes an isostructural phase transition at 13.1 GPa, which is responsible for the abnormal change in resistance.By fitting the volume data with the Birch–Murnaghan equation of state, we found that the bulk modulus B0 of the Y2 O3/ZrO2 solid solution increases by 131.9% from 125.2 GPa to 290.3 GPa due to the pressure-induced isostructural phase transition.
