Investigation on the structural and electrical behavior of bioactive Ca10(PO4)6(OH)2 - K0.5Na0.5NbO3 ceramic

The present study explores the structural, electrical and preliminary bioactivity of Ca-10(PO4)(6)(OH)(2) (HAP) - K0.5Na0.5NbO3 (KNN) composites. The composites and monoliths of KNN and HAP are synthesized individually by the sol-gel and solid-state routes. The composites have been prepared by varying their At. % (20, 40, 60, and 80%). The purity of composite formation with the presence of both hexagonal and orthorhombic phases for HAP and KNN respectively without any reaction between monoliths was observed through the X-Ray diffraction (XRD) and Raman spectroscopy. The optical band-gap (E-g) is studied using the UV/VIS/NIR spectroscopy that shows the major contribution of oxygen and OH vacancies towards the decrease of the bandgap. The morphology depicts the presence of both the nano-sized HAP and coarse KNN grains. The KNN grains are larger than HAP grains and a systematic variation is observed in composites with increasing At.% of KNN. The dielectric and impedance studies are carried out in the frequency range of 100 Hz-1 MHz. The dielectric constant (epsilon(r)) lies between 20 and 40 measured at 100 kHz. The ionic behavior of HAP contributed to the dielectric phenomenon, and an increase in epsilon(r) leads to conductivity. The impedance analysis draws a picture of the conduction phenomenon and the relaxation mechanism prevalent within the composites. The frequency-dependent ac conductivity (sigma(ac)) curve follows Jonscher's universal power law. The comprehensive study of KNN - HAP bioceramic composites and understanding the electrical properties can open up possibilities for their applications in biomedical engineering.