Breaking of inversion symmetry in NdGaO3

$\mathrm{NdGa}{\mathrm{O}}₃$ (NGO) is an important substrate material often used in depositing functional oxide thin films. We have carried out temperature-dependent polarized Raman and infrared spectroscopy studies along with theoretical calculations on single-crystal NGO, which revealed a structural phase transition from centrosymmetric space group Pbnm to noncentrosymmetric space group $Pbn{2}₁$ at \ensuremath{\sim}200 K. The microscopic origin of the phase transition is extracted using a unique protocol involving polarized Raman spectroscopy (PRS) studies carried out as a function of crystallographic orientation. Here, we demonstrate the power of PRS in probing directional atomic rearrangements across the phase transition.