Enhancing the zircon yield through the addition of calcium phosphates into ZrO2–SiO2 binary systems: synthesis and structural, morphological, mechanical and in vitro analysis†

The crystallization of ZrSiO₄ is generally accomplished by the addition of mineralizers into ZrO₂–SiO₂ binary oxides. The current investigation aimed to investigate the effect of adding calcium phosphates into ZrO₂–SiO₂ binary oxides on the yield of ZrSiO₄. The concentration of calcium phosphate additions were varied to obtain ZrSiO₄ that fetches improved mechanical and biological properties for application in hard tissue replacements. The findings highlight the significant role of Ca²⁺ and P⁵⁺ in triggering the ZrSiO₄ formation via their accommodation at the Zr⁴⁺ and Si⁴⁺ sites. Especially, calcium phosphate additions trigger the t- → m-ZrO₂ transition beyond 1000 °C, which consequently reacts with SiO₂ to promote ZrSiO₄ formation. Calcium phosphates are accommodated at the lattice sites of ZrSiO₄ with a maximum limit of 20 mol%, beyond which the crystallization of β-Ca₃(PO₄)₂ is noticed. The optimum amount of 20 mol% of calcium phosphates displayed a better strength than that of all the investigated specimens. More than 80% of cell viability in MG-63 cells was invariably determined in all the calcium phosphate-added ZrSiO₄ systems.