Transmission electron microscopy and x-ray diffraction data show that rapid thermal anneals of SrS:Ce thin films enhance grain size and reduce crystalline defects. Electron paramagnetic resonance results suggest that these anneals lead to less variance in the crystal field environments at the nearly cubicCe3+sites along with the formation of another type ofCe3+site believed to involve a nearby Sr vacancy. We suggest that the association ofCe3+sites withVSrshifts the electroluminescence towards larger wavelengths as the symmetry of the activator site is lowered. ©1997 American Institute of Physics.