Piezoelectricity in Sr Doped Thick Films of Hydroxyapatite

The current study reports the synthesis, characterization and tape casting of strontium substituted into the calcium sublattice of hydroxyapatite in range of (0-100 mol%). The XRD powder data reveals that a primary HAp phase as well as secondary Ca-3(PO4)(2) (beta-TCP) phase coexist. Our analysis shows that Sr+2 preferentially occupies the HAp lattice sites rather than beta-TCP. Developed free-standing tapes of HAp offer unique possibility of custom designed solutions for biomedical applications by controlling shape size and tuned electrical properties. We report piezoelectricity in Sr doped hydroxyapatites thick films, the piezoelectric coefficient is an order of magnitude higher than what has been previously obtained in PLD deposited hydroxyapatite films [15]. The piezoelectricity shows slight improvement with the Sr doping. Despite low piezoelectric coefficient, the generated voltage is of the order of mV which is high enough to have physiological relevance since the resting potential of the cells lie between 60-90 mV. Further improvements in the material design and poling could pave way to understand the role of electricity in bone growth and to use piezoelectric energy harvesting to tune spinal and neuro stimulators.