Improved functional response of spark plasma sintered hydroxyapatite based functionally graded materials: An impedance spectroscopy perspective

Abstract

Owing to the inherent polarization regulated functionality of living bone, the present study aims to enhance the polarizability of hydroxyapatite (HA) without affecting its’ surface chemistry i.e., excellent biocompatibility. This concept has been materialized by the development of functionally graded materials (FGMs) using perovskites BaTiO 3 and CaTiO 3 as intermediary layers. These perovskites were sandwiched between HA layers via buffer interlayers to provide the structural integrity to the FGMs. FGMs were optimally processed using spark plasma sintering route at 1100°C for 10 min. Microstructural analyses of fractured surfaces revealed no sign of delamination between HA/BaTiO 3 or HA/CaTiO 3 layers, despite of differences in their coefficients of thermal expansions. Further, detailed impedance spectroscopic analysis was performed over a wide range of temperature (35–500°C) and frequency (1 Hz - 1 MHz). Almost two times increase in polarizability has been observed in both types of FGMs as compared to HA. Overall, the developed FGMs can be suggested as potential materials for polarized bone applications. © 2019 Elsevier Ltd and Techna Group S.r.l.