Combinatorial property mapping of Titanium-Zirconium thin film libraries as screening for medical material candidates

By employing a co-sputtering technique, combinatorial thin film libraries in the Ti–Zr system are produced. The libraries have a compositional spread ranging from 40 to 70 at% Ti. The confocal geometry of the sputtering system is maintained for the production of all thin films. The microstructural and crystallographic properties are elucidated by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis. Furthermore, contact angle measurements and nanoindentations are performed to map the wettability, hardness, and elastic modulus of the alloy system. The electrochemical properties, i.e., the oxide film formation factor and the relative permittivity of anodically grown oxides on the parent metal alloys are determined. The measurements are performed in phosphate-buffered saline in order to best simulate a biological environment. A linear shift in the properties is observed along the compositional gradient for the EDX, XRD, and SEM analysis. For all other sets of measurements deviations from the linear behavior, are observed around the 60 at% Ti concentrations. This coincides with the formation of a congruent alloy in bulk material. The observed changes however, deviated also from expectations for bulk alloys. The implications and potential for those alloys as implant material are discussed in the following.