Elucidating the Phase Transformation and Metallization Behavior of Zinc Phosphide under High Pressure.

Among the family of IIV-type compounds, zinc phosphide (ZnP) occupies a unique position. As one of the most promising semiconductors well-suited for photovoltaic applications, ZnP has attracted considerable attention. The stability of its structure and properties are of great interest and importance for science and technology. Here, we systematically investigate the pressurized behavior of ZnP using in situ synchrotron radiation angle-dispersive X-ray diffraction (ADXRD) and in situ electrical resistance measurement under high pressure. The ADXRD experiment shows that ZnP undergoes an irreversible structural phase transition under high pressure, beginning at 11.0 GPa and being completed at ∼17.7 GPa. Consistently, the high-pressure electrical resistance measurement reveals a pressure-induced semiconductor-metal transition for ZnP near 11.0 GPa. The kinetics of the phase transition is also studied using in situ electrical resistance measurement and can be well described by the classical Avrami model. What's more, the new high-pressure structure of ZnP is refined to be orthorhombic with space group ; the lattice parameters and bulk modulus of this high-pressure phase are determined as = 3.546 Å, = 5.004 Å, = 3.167 Å, and = 126.3 GPa. Interestingly, we also predict a possible structural phase transformation of orthorhombic phase () to cubic phase (432) during the decompression process; this cubic ZnP is metastable at ambient conditions. These experimental results reveal the unexpected high-pressure structural behaviors and electrical properties of ZnP, which could help to promote the further understanding and the future applications of ZnP as well as other IIV compounds.