Synthesis and characterization of calcium hydroxyapatite (Hap) and Ti(IV)-substituted Hap particles by forced hydrolysis of Ca(OH)₂–Na₄P₂O₇ solution

The productions of calcium hydroxyapatite (Hap) and Ti(IV)-doped Hap (TiHap) particles were examined by forced hydrolysis reaction of Ca(OH)2-pyrophosphate (pp: P2O7) and Ca(OH)2-pp-TiCl4 mixed solutions under 100 and 140°C, respectively, and precipitated particles were characterized by various physicochemical techniques. The degree of hydrolysis of pp ions was remarkably improved and the yields of the precipitates by using the pp ions was increased rather than the tpp one. No particles were produced at higher concentration of pp ions. On the other hand, ellipsoidal aggregated and rod-like particles were produced at other concentration domains. The Hap particles produced were ellipsoidal secondary particles with ca. 210­240 nm in the particle length which were composed by aggregation of small primary single crystal particles with ca. 20­50nm in length. The TiHap particles facilitated at atomic ratio of Ti/(Ca+Ti) [XTi] 1⁄4 0.20 were ellipsoidal secondary particles with ca. 240­380nm in length composing by aggregation of small primary particles with ca. 30­100nm in length, while they were changed to very fine particles with ca. 5­10 nm in diameter along with small amounts of large rod-like particles at XTi = 0.3. The highly crystallized pure TiHap particles were produced at XTi 1⁄4 0.15, while the Hap structure was almost disappear at XTi = 0.2. All the TiHap particles produced at XTi ̄ 0.2 were phosphorus deficient. The diffuse reflectance UV spectra of TiHap particles revealed that these particles have a UV absorption property, especially fabricated at XTi = 0.05. The highly crystallized TiHap particles (0.05 1⁄4 XTi 1⁄4 0.15) had also large specific surface area. ©2016 The Ceramic Society of Japan. All rights reserved.