This paper studies the effect of porosity on the electrical properties and polarisation behaviour of hydroxyapatite based ceramics prepared in both dense and porous form. Porosity was introduced into the hydroxyapatite using either burnt-out polymer spheres to produce isolated pores or using polymer foams to create interconnected porosity. The samples were sintered in water vapour at 1300C and polarised at 400C with a dc voltage of 3kV/cm applied for 1 hour. Thermally stimulated depolarisation current measurements were used to investigate the degree of polarisation of the hydroxyapatite ceramics and dielectric spectroscopy used to measure the ac conductivity of the materials at the polarisation temperature. The porous materials were successfully polarised and the presence of a high surface area to volume ratio in the porous samples was thought to increase the level of polarisation.
Gittings, J. P., Bowen, C. R., Dent, A. C. E., Turner, I. G., Baxter, F. R., Cartmell, S., & Chaudhuri, J. (2009). Influence of porosity on polarisation and electrical properties of hydroxyapatite based ceramics. Ferroelectrics, 390(1), 168-176. https://doi.org/10.1080/00150190903001011