Synthesis of partially stabilized leucite Original Research Article

Leucite is the dominating crystalline phase in most feldspathic dental porcelains used for ceramic-fused-to-metal restorations. The stable form of leucite at room temperature is a tetragonal one, which undergoes a phase transition to cubic form at 625 °C. This transformation is associated with 1.2% volume contraction that leads to the formation of microcracks in and around the crystals. The high amount of tetragonal leucite crystals may be the reason of developing large flaws within the glass matrix that would lead to a decrease of mechanical properties. Potentially, cesium-stabilized cubic leucite could be added to leucite porcelains to increase crystalline content without increasing flaw size and frequency. The aim of this work was to develop a suitable and reproducible technology for the preparation of cubic leucite. Previously, the hydrothermal synthesis of tetragonal leucite was described. This method was modified for the preparation of cubic leucite. It was found that the final products consist of both tetragonal and cubic leucite up to 9.52 mol% of Cs2O. Above this value fully stabilized leucite was observed. It was proved that the products of the hydrothermal syntheses are formed by spherolites having particle size of approximately 2 μm that consist of particles tens of nm in size.