Epitaxial growth of gehlenite in CaO-MgO-Al2O3-SiO2 based glass ceramic induced by Nb2O5 addition

In this study, the crystallization behavior of a CaO-MgO-Al2O3-SiO2 based glass ceramics with Nb2O5 addition was investigated by using DSC, XRD and TEM techniques. It was found that three crystalline phases, namely, CaNb2O6, diopside and Gehlenite (Ca2Al2SiO7), were formed from the glass matrix during the crystallization heat treatment. The CaNb2O6 phase was the first to precipitate from the glass matrix at around 850°C, acting as a nucleating agent that facilitated the formation of Gehlenite (Ca2Al2SiO7) at 900-950°C. The TEM observation revealed a consistent orientation relationship between the CaNb2O6 and the Gehlenite (Ca2Al2SiO7) phases, indicating that CaNb2O6 could induce the epitaxial growth of Gehlenite (Ca2Al2SiO7). This result provides a new insight into the preparation of Gehlenite epitaxial films and glass ceramics.