Effect of water on piezoelectric, dielectric, and elastic properties of bone

The complex piezoelectric constant ( d = d ′ − id ″), elastic constant ( c = c ′ + ic ″), and dielectric constant (ε = ε′ − i ε″) were measured at a frequency of 10 Hz over the temperature range from −150 to 50°C and for a range of hydration up to 0.26 g/g for decalcified bone and up to 0.084 g/g for bone. For decalcified bone, ε′ and ε″ increased with increasing hydration with a deflection at the critical hydration h c = 0.08 g/g; d ′ at −150°C increased below h c but decreased above h c with increasing hydration; c ′ increased below −60°C but decreased above −60°C with increasing hydration; and the peak temperatures of ε″, d ″, and c ″ below −50°C agree with each other and decreased with increasing hydration with a deflection at h c . For bone, similar hydration and temperature dependences were observed for ε and c . However, the dependence of d on hydration and temperature was different from that of decalcified bone, reflecting a two‐phase structure consisting of collagen fibers and mineral hydroxyapatite. The critical hydration for bone was 0.04 g/g.