6533b7d1fe1ef96bd125d59d

RESEARCH PRODUCT

Effect of High Pressure on the Crystal Structure and Vibrational Properties of Olivine-Type LiNiPO4

subject

description

In this work, we present an experimental and theoretical study of the effects of high pressure and high temperature on the structural properties of olivine-type LiNiPO4. This compound is part of an interesting class of materials primarily studied for their potential use as electrodes in lithium-ion batteries. We found that the original olivine structure (α-phase) is stable up to ∼40 GPa. Above this pressure, the onset of a new phase is observed, as put in evidence by the X-ray diffraction (XRD) experiments. The structural refinement shows that the new phase (known as β-phase) belongs to space group Cmcm. At room temperature, the two phases coexist at least up to 50 GPa. A complete conversion to the β-phase was only obtained at high-pressure and high-temperature conditions (973 K, 6.5 GPa), as confirmed by both XRD and Raman spectroscopy. Ab initio calculations support the same structural sequence. The need of high-temperature conditions to obtain the complete transformation of the α-phase into the β-phase...