An estimate of the critical grain size for microcracks induced in hydroxyapatite by thermal expansion anisotropy

Abstract

Hydroxyapatite (HAp) is a bioactive ceramic material with a variety of current and potential applications in medical technology. HAp is noncubic and, thus, should be subject to microcracking due to thermal expansion anisotropy (TEA) if the grain size, G> G cr, the critical grain size for TEA-induced microcracking. However, no estimates of G cr are available in the literature. Although a range of thermal expansion values reported in the literature complicates the estimation of G cr for HAp, a G cr of 1.1 μm for polycrystalline HAp is estimated using data from the literature and from the authors' measurements.