@article{WANG2025, 
author = {Yue WANG and Chaowen XU and Ying LI and Jing GAO},
title = {Phase Transition of α-FePO4 under High Pressure: A Raman Spectroscopy Study},
year = {2025},
journal = {Chinese Journal of High Pressure Physics},
volume = {39},
number = {10},
keywords = {α-quartz, orthophosphate, diamond anvil cell, Raman spectroscopy, phase transition},
url = {https://www.sciopen.com/article/10.11858/gywlxb.20251100},
doi = {10.11858/gywlxb.20251100},
abstract = {Given the topological isomorphism between α-FePO4 and α-quartz, this study employed a diamond anvil cell coupled with Raman spectroscopy to examine the phase transition of α-FePO4. The structural evolution across a pressure range of 0.2−27.3 GPa was delineated into three stages. At 2.8−3.6 GPa, α-FePO4 initiates a phase transition, achieving a complete transformation to FePO4-Ⅱ at 4.6 GPa. Between 4.6−27.3 GPa, the (meta) stability of FePO4-Ⅱ is predicated on the cooperative deformation of the adaptable [FeO6] octahedra and the rigid [PO4] tetrahedra. The progressive increase in structural disorder and the slowing of vibrational frequency shifts signify a transition to a non-linear compression regime. Notably, in the 9.8−11.1 GPa threshold, discontinuous variations in P―O bond lengths and mode widths serve as evidences of pressure-induced heterogeneous strain within the [FeO6]-[PO4] network, suggesting entry into a metastable region. Upon decompression to 4.6 GPa, FePO4-Ⅱ exhibits partial recovery of structural order, maintaining metastability at ambient conditions, which underscores its unique pressure memory characteristics. This study demarcates the stability boundary of α-FePO4, elucidates the fundamental mechanisms underpinning stability in orthophosphates, and forecasts structural evolution pathways. The findings offer insights into high-pressure dynamic response of quartz-like minerals.}
}