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

Among the family of II₃V₂-type compounds, zinc phosphide (Zn₃P₂) occupies a unique position. As one of the most promising semiconductors well-suited for photovoltaic applications, Zn₃P₂ 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 Zn₃P₂ 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 Zn₃P₂ 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 Zn₃P₂ 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 Zn₃P₂ is refined to be orthorhombic with space group Pmmn; the lattice parameters and bulk modulus of this high-pressure phase are determined as a = 3.546 Å, b = 5.004 Å, c = 3.167 Å, and B₀ = 126.3 GPa. Interestingly, we also predict a possible structural phase transformation of orthorhombic phase (Pmmn) to cubic phase (P4₂32) during the decompression process; this cubic Zn₃P₂ is metastable at ambient conditions. These experimental results reveal the unexpected high-pressure structural behaviors and electrical properties of Zn₃P₂, which could help to promote the further understanding and the future applications of Zn₃P₂ as well as other II₃V₂ compounds.