Synthesis and characterization of an amorphous precursor for leucite dental ceramics

Development of a new preparation technology of leucite (KAlSi 2 O 6 ) dental ceramics is one of the most pursued goals in a present research of dental materials. Preparation procedure of leucite from an amorphous precursor was proposed in our previous work. The aim of this study was to investigate the synthesis of the precursor and to determine its optimal conditions. Leucite precursors were prepared by hydrothermal synthesis in a Teflon-lined stainless steel autoclave. The role of principal factors influencing its synthesis (composition of a reaction mixture, reaction temperature and time) was described. Crystallization properties of prepared precursors to form leucite were characterized by differential thermal analysis (DTA) and by X-ray powder diffraction (XRD) analysis of the calcinated samples. The research showed that leucite crystallizes only from precursors prepared at a specific interval of conditions. The optimal conditions for the precursor synthesis were determined as follows: at 150 °C, 2–6 h, at 200 °C, 1–2 h of the hydrothermal treatment; amorphous SiO 2 powder as the silica source and Al powder as the aluminum source; silica/alumina ratio equal to 3 or 3.5 and 3 M KOH solution.