Amorphous Si1-xGex films, with a varying germanium. fraction, were deposited using radio frequency (r.f.) sputtering and annealed under different conditions to form polycrystalline films. The structural properties of the films were examined using X-ray diffraction (XRD) and Raman spectroscopy. From the XRD and Raman spectra, the crystallinity of the films was observed to improve with an increase in annealing temperature and duration, and with increasing germanium fraction. An anomalous retardation in the crystallisation rate was attributed to the presence of impurities within the films. The impurities, together with an increased nucleating site density, caused a significant reduction in the extracted grain size.