Preparation of needle‐like hydroxyapatite by homogeneous precipitation under hydrothermal conditions

Abstract
Preparation of hydroxyapatite was carried out by a homogeneous precipitation technique using hydrothermal reactions of Ca(EDTA)2‐ and PO43‐ at 130–250°C and pH 4–10. Hydroxyapatite and monetite were formed above pH 6 and below pH 4, respectively. Needle‐like hydroxyapatite was formed at high temperatures above 130°C. The length of the needle‐like hydroxyapatite crystal increased with increasing working solution pH and temperature.