Alternating current electric field modified synthesis of hydroxyapatite bioceramics

This study presents an innovative approach towards wet chemical synthesis of hydroxyapatite bioceramics by application of alternating current (AC) electric field during the synthesis at low and intermediate temperatures. Specially designed low-cost electrical setup provided stable, reliable and modular system which supplied electric energy within the reaction volume as characterized by computer simulation of reaction conditions. Energy introduced through external excitation (alternating voltage amplitude of 10 V and frequency of 1 kHz) influenced crystallization, ionic composition, sintering behavior of hydroxyapatite powders, microstructure and final phase composition of sintered ceramics. Crystallite size in [002] crystallographic direction increased with electric field assistance regardless of the synthesis temperature. Non-isothermal sintering studies showed significantly improved densification and implied better thermal stability of powders synthesized in the presence of AC field, shifting the Ca/P ratio towards stoichiometric one. Vibrational spectroscopy analysis indicated the role of charge, mobility and effective ionic radius of present ions in transferring the energy supplied with external field influencing further thermal stability of the crystal lattice. Microstructural investigation and phase composition analysis suggested that application of AC electric field during the synthesis of nanocrystalline hydroxyapatite improved material properties and offered potential for tailoring macro/micro-porosity with precise modulation of electrical parameters.