Investigation of Antisite Defect Formation and Chemical Expansion in LiNiPO by in Situ Neutron Diffraction.

In situ neutron diffraction was used to characterize the effect of temperature on the crystal structure of LiNiPO. LiNiPO adopts an ordered olivine structure at room temperature, but, with increasing temperature, this work shows that a significant amount of Li and Ni cation exchange occurs, for example, ∼15% at 900 °C. The antisite disorder is detected by residual nuclear densities on the M1 and M2 octahedral sites in the olivine structure using difference Fourier maps and by changes in cation site occupancies, lattice parameters, and mean ⟨M-O⟩ bond distances.