Synthesis and characterization of mullite-zirconia prepared through solid sintering of 3Al₂O₃-2SiO₂ xerogel and ZrO₂ xerogel as a dental implant material

Mullite-zirconia is a ceramic material that has mechanical properties values that are close with the jaw bone. Lately, various precursor characteristics were used to produce the mullite-zirconia as the starting material. However, the processing requires a higher temperature to achieve crystallization and densification of mullite-zirconia. In this study, mullite-zirconia was synthesized through solid sintering of 3Al₂O₃−2SiO₂ xerogel and ZrO₂ xerogel. Those xerogels were produced by the sol-gel method and characterized by particle size analyzer and scanning electron microscope. Subsequently, those xerogel were categorized into five batch composition (AlSi, Zr, 85AlSi/15Zr, 80AlSi/20Zr and 75AlSi/25Zr). These samples were then sintered at 1300 °C for 2 hours and characterized by X-ray diffraction. The result shows the acquired particle size of 3Al₂O₃−2SiO₂ xerogel and ZrO₂ xerogel are 355.7 nm and 414.3 nm respectively. The morphology of these samples are irregular, however, for ZrO₂ xerogel, it has angular morphology in some particles. The XRD exposed AlSi turn into 100% mullite. Meanwhile, Zr produces 22% tetragonal zirconia and 78 % monoclinic zirconia. For 85AlSi/15Zr, it contains mullite and monoclinic zirconia with fraction amounts are 74.4 % and 25.6 % respectively. Subsequently, 80AlSi/20Zr shows the lower fraction amount of mullite crystallinity (71.5 %) along with increasing the amount of monoclinic zirconia (28.5%). Lastly, 75AlSi/25Zr shows the crystallinity of sillimanite, tridymite and monoclinic zirconia with the fraction amount are 57.3 %, 12.1%, 30.6 % respectively. We conclude the reduction in the number of zirconia is able to maintain the mullite crystal, however, along with the increase in zirconia, it inhibits the formation of the mullite structure due to Zr atom act as an inhibitor in substitution of Al with Si atom to form the mullite crystalline.