Influence of molecular water dynamics on the electrical conductivity of hydrothermally synthesized hydroxyapatite from cuttlefish bone

Abstract

Hydrothermal transformation of natural aragonitic cuttlefish bones (Sepia officinalis) was used to successfully create hydroxyapatite nanoparticles (Ca₁₀(PO₄)₆(OH)₂), which were then completely studied using XRD, FTIR, and broadband dielectric spectroscopy (BDS). In this work, the electrical characteristics of hydroxyapatite are thoroughly examined throughout a wide frequency range (0.1 Hz to 1 MHz) and low temperature range (253 K to 473 K). While the DC conductivity shows characteristic non-Arrhenius behavior that is highly connected with thermal and spectroscopic investigations (FTIR, DSC, and TGA), the AC conductivity results show excellent agreement with both Almond-West formalism and Jonscher's universal power law. The dual conduction mechanisms controlled by the correlated barrier hopping (CBH) and non-overlapping small polaron tunneling (NSPT) models are confirmed by the temperature dependence of the frequency exponent s. Additionally, the AC conductivity data was used to extract important charge transport metrics, such as hopping energy, density of states at the Fermi level, and hopping distance. Deeper understanding of the intricate conduction pathways in hydroxyapatite is possible through the use of complementary impedance spectroscopy and Nyquist plot investigations. The crucial importance of charge carrier interactions and polaron dynamics in the conduction mechanism of biogenic hydroxyapatite is highlighted by this thorough electrical characterization, which paves the way for its optimal utilization in electronic and medicinal applications.