Piezoelectric and mechanical properties of hydroxyapatite/titanium oxide composites

Hydroxyapatite (HAp) is the most common bioactive ceramic used to replace hard tissue in the body. Because of its low resistance and fragile nature, more attention is being given to composites based on HAp such as HAp/TiO2 composites. This study aims at reporting the synthesis of HAp/TiO2 composites (hereafter named HT composite) by sol-gel and co-precipitation methods assisted by ultrasonic radiation. The structural characterization was carried out by X-ray Diffraction (XRD) and Scanning Transmission X-ray Microscopy (STXM) techniques using synchrotron radiation, which allowed a mixture of phases to be identified separately in the two materials once the composite was formed. A Rietveld refinement for XRD data determined the phase percentage and structural parameters obtained for each material. In addition, crystallite size using the modified Scherrer equation was determined. A piezoelectric character of the two materials was confirmed by Piezoresponse Force Microscopy (PFM) to determine the piezoelectric coefficient (deff). Finally, PinPoint-AFM force curves confirmed an increase in the Young's modulus value for the HT composite.