Ferroelectric to paraelectric transition in YCrO$_{\mathrm{3}}$ revisited

X-ray diffraction (XRD) and Raman spectroscopy measurements are used to explore the origin of ferroelectricity in the orthorhombic ferroelectric oxide ,YCrO$_{\mathrm{3}}$. Temperature dependent XRD studies carried out up to 900K and subsequent Reitveld refinement of the data shows that there is no evidence of any structural phase transition in YCrO$_{\mathrm{3}}$ across the ferroelectric to paraelectric phase transition at T$_{\mathrm{c}} \quad =$ 470K. Temperature dependent unpolarized Raman spectroscopy measurements, from 300 K to 600 K, were carried out to investigate structural changes near Tc locally within the material. All Raman modes below 600 cm$^{\mathrm{-1}}$ were assigned to phonon modes of Pnma structure and for further analysis of the Raman data, the line shape parameters were obtained by fitting a Lorentzian function to each peak. Surprisingly, despite absence of observation of any structural change in XRD measurements,YCrO$_{\mathrm{3}}$ shows a strong anomalous temperature variation near T$_{\mathrm{c}}$ in the peak positions and line widths for selected modes as a function of temperature. It is believed that YCrO$_{\mathrm{3}}$ is an improper ferroelectric and ferroelectricity arises due to local rotations of CrO$_{\mathrm{6}}$ octahedra leading to non-centrosymmetricity. Our results seem to suggest that YCrO$_{\mathrm{3}}$ undergoes an iso-structural transition across T$_{\mathrm{c}}$.