Variable Range Hopping in SrTiO3–Ca10(PO4)6(OH)2 Bio-Ceramic Composites

We investigate the electrical properties in ceramics, focusing primarily on the conductivity mechanisms crucial to bio-electrets' service life. A biocompatible ceramic composite of varying concentrations of SrTiO₃ (ST) and Ca₁₀(PO₄)₆(OH)₂ (HAP) is developed. By X-ray diffraction, we establish the microstructural and phase evolution of the bio-composites. The crystallite sizes are found to increase with the increasing concentration of ST in the composites. The composites' micrograph reveals the presence of pores, and the grain sizes calculated from it are found to follow a trend similar to the crystallite size. The conduction mechanisms in the composites are studied to explore the composites' electrical properties from the perspective of biological applications. The conductivity is very low (≃10^-8 S/cm), and the porous structure of the composites revealed from the micrographs is one of the factors for such low conductivity. From a plethora of conduction mechanisms, Motts' variable range hopping (VRH) conduction is projected as the most appropriate mechanism that appropriately describes the conduction process in the composites. Motts' VRH is also related to the polarization mechanism associated with the development of electrets. Our study points toward the practical potential of applying the designed bio-composites in generating bio-electrets or understanding the electrical properties that are at the forefront of research in designing electro-active smart scaffolds for bone tissue engineering applications.