Fabrication of Sodium-Substituted Hydroxyapatite Ceramics via Ultrasonic Spray-Pyrolysis Route and their Material Properties

Abstract

Biological apatite presented in bone and teeth of mammals contains various ions in trace levels. Substitution of the ions into hydroxyapatite (HAp) can ensure higher bioactivity compared with stoichiometric HAp. It is known that sodium (Na) has been detected as an abundant trace element next to the presence of calcium and phosphorous in natural bone. The aim of this study is to examine the effect of substitution of Na on material properties of the HAp ceramics. Therefore, we have synthesized the sodium-substituted hydroxyapatite (NaAp) ceramics without carbonate ions by an ultrasonic spray-pyrolysis (USSP) technique. The USSP technique can obtain the desired powder by directly heating droplets of a sample solution with the target composition. Both NaAp powders with (Ca+Na)/P ratios of 1.67, 1.72 and 1.77 and their ceramics did not contain carbonate ions, and HAp single phase was maintained even after sintering. It was revealed that the substitution of Na enhanced the sinterability of HAp ceramics and improved the apatite-forming ability.