Raman scattering, Stokes photoluminescence (PL) spectroscopy and differential scanning calorimetry (DSC) measurements have been used to study the phase transition of 2 mol% erbium-doped potassium niobate (KNbO3) polycrystalline. The low-temperature Raman scattering experiments showed that the phase transition occurred at around 200 and 300K, and the DSC thermograms indicated that the phase transition occurred at 203, 290, 481 and 666K, respectively. Comparing our results with Matthias's, we proposed that 2 mol% erbium-doped KNbO3 polycrystalline exhibits a new phase transition at 203K. The PL spectra intensity was also unusual during these temperatures; a strong non-exponential behavior was found. From these results of Raman scattering, DSC and PL, we concluded that the behavior of 2 mol% erbium-doped KNbO3 polycrystalline at 203K should be a new phase transition. (c) 2005 Elsevier B.V. All rights reserved.