The main focus of this research is to show, through the use of perturbed angular correlation spectroscopy (PAC), that a displacive phase change occurs in the mineral zirconium silicate, ZrSiO4, which is related to the purity of the sample. This phase change is known to exist in pure naturally occurring zircon, which has low levels of impurities and radiation damage. This subtle phase change occurs in the mineral occurs around the annealing temperature of 800°C. In order to obtain an extremely pure crystal, a synthetic ZrSiO4 crystal is made. Once the phase change is shown to exist in the synthetic ZrSiO4, the theory that the phase change is dependent upon the purity of the sample will be reconfirmed by performing the same experiments using a synthetic sample of hafnon, HfSiO4. Zircon and hafnon share many of the same physical and chemical properties and should behave the same under the performed tests. The observation of the phase change is performed by using the measurable electric field gradient parameters obtained from PAC spectroscopy. X-ray diffraction (XRD) spectroscopy is used after the production of the synthetic samples to determine the relative purity of both samples. Both samples were run under the same conditions and both do exhibit the phase change at a temperature shortly following the annealing temperature. As shown in this work these phase changes are seen in the pure synthetic samples, and as shown in previous work, are only present in naturally occurring samples that have low levels of impurities.