Thermal behavior of porcine biogenic hydroxyapatite: An in-situ impedance spectroscopy study

This paper studies the electrical properties of porcine bone through in-situ impedance spectroscopy (IS) from 50 Hz-5 MHz at temperatures from room temperature to 1273 K. Also, other in-situ techniques, such as Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), High-Temperature X-ray diffraction (HT-XRD), and ex-situ complementary techniques, such as Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM), were carried out to explain the physicochemical transformations of the system. The conduction phenomena in biogenic hydroxyapatite are governed by intergranular contact and crystal size. A thermal phase transition occurs at about 973 K that DSC, HT-XRD, and IS can detect. The correlation between these techniques indicates that this transition is a coalescence phenomenon that generates a nano to microcrystal size transition and out-diffusion of Mg to the surface. These processes improve the crys-talline quality and change the activation energy for each thermal cycle, showing a strong correlation between structural and electrical properties. Electrical modulus, electrical permittivity, and electrical conductivity are sensible to this structural change.

Automated summary

This paper investigates the electrical properties and physicochemical transformations of porcine bone through in-situ impedance spectroscopy and complementary techniques. The conduction behavior in biogenic hydroxyapatite is influenced by intergranular contact and crystal size. A thermal phase transition at around 973 K is detected, which involves changes in crystal size and out-diffusion of Mg to the surface. The correlation between structural and electrical properties is evident.