Preparation and sintering of CaSiO₃ from coprecipitated powder using NaOH as precipitant and its apatite formation in simulated body fluid solution

CaSiO₃ powders were prepared from an ethanol solution dissolving Ca(NO₃)₂ · 4H₂O and Si(OC₂H₅)₄ by the coprecipitation method using various concentrations of NaOH as precipitants. Some Na component remained in the precipitates without washing and strongly affected the characteristics of the resultant powders, but the Na residue was removed by a washing treatment. The precipitate prepared by using 0.33 mol/l of NaOH and twice-washing contained the lowest amount of Na residue. It was calcined at 500 and 900 °C, respectively, to crystallize CaSiO₃ phase and ground by a planetary potmill. The ground CaSiO₃ powder was sintered to about 89% theoretical density by firing at 1400 °C. By soaking the CaSiO₃ sintered bodies in simulated body fluid (SBF) solution for various times, an hydroxylapatite (HAp) layer formed as aggregates of ball-like particles on the surface of the CaSiO₃ sintered bodies after soaking for a short period; thereby, the CaSiO₃ ceramics is suggested to have very good biocompatibility.