The structural and electrical transport behaviors of CuInS2 nanocrystals under high pressure have been investigated using angle dispersive X-ray diffraction (ADXRD), in situ Hall effect, and temperature-dependent electrical resistivity measurements. A pressure-induced irreversible structure transformation from tetragonal phase to cubic phase has been confirmed at 10.9 GPa, which has noticeably elevated the transition pressure (1.4 GPa) in nanocrystals compared to the bulk CuInS2. In addition, the pressure-dependent electrical transport parameters, such as Hall coefficient, Hall mobility, carrier concentration, and electrical resistivity, all show dramatic changes around 11 GPa, implying that the pressure-induced structure transformation of CuInS2 can bring about a series of changes in the carrier transport properties. Specifically, the sign of the Hall coefficient is changed from negative to positive around 12 GPa, implying that CuInS2 undergoes a carrier-type inversion from n- to p-type. In addition, the temperature-dependent electrical resistivity reveals that CuInS2 is still a semiconductor after the phase transition but with an opposite trend in the variation of the activation energy for the ambient and high-pressure phases.

The structural and electrical properties of CaB4 under high pressure have been studied by angle dispersive X-ray diffraction, in situ Hall effect measurement, and first-principles calculations. An abnormal change of the c/a ratio was observed around 12 GPa in the experiments and backed by theory calculation, indicating an isostructural phase transition. Unlike other materials, the analysis of the electronic and phonon band structure doesn't reveal an electronic topological transition or phonon softening supporting this phenomenon. While the subtle changes in the electron band dispersions at the Fermi surface shown by the measurements of the resistivity, Hall coefficient, carrier concentration, mobility, and temperature-dependent resistivity can explain the anomaly in the c/a ratio. The study of electrical transport properties provides strong support for the occurrence of the isostructural phase transition in CaB4.

The structural and electrical properties of ZnV2O6 under high pressure have been studied using Raman spectroscopy, in situ angle dispersive X-ray diffraction (ADXRD), and alternating current (AC) impedance spectroscopy. The results of Raman spectra indicate that ZnV2O6 undergoes a reversible structural change around 16.6 GPa, as evidenced by the appearance of new peaks. The results of Rietveld refinements from in situ ADXRD data indicate that the monoclinic symmetry (C2/m) is retained up to 16.0 GPa and the C2 phase comes to coexist between 16.0 and 16.9 GPa. Above 16.9 GPa, the high-pressure phase can be distinguished only as the C2 structure. The transformation process from the C2/m phase to the C2 phase is mainly caused by the more distorted ZnO6 octahedra and VO6 octahedra at higher pressures. The equal bond distances Zn–O2 and V–O3 in the C2/m phase become unequal in the C2 phase. Furthermore, the measurements of the AC impedance spectroscopy of ZnV2O6 reveal obvious changes in its electrical transport properties at 14.1 GPa which could correspond to the observed phase transition in the Raman and ADXRD measurements. The combined analyses of experimental results suggest the occurrence of a reversible structural phase transition of ZnV2O6 around 16.0 GPa.