Study of Fe2O3-ZrO2 interface of ZrO2 coating grown by hydrothermal process on stainless steel

Abstract

Thin films of tetragonal ZrO2 have been grown on α-Fe2O3 coated stainless steel substrates by hydrothermal process using zirconyl nitrate and ethylenedinitrilotetraacetic acid disodium salt dihydrate. At the initial stage of the film formation, Na salt of Zr-EDTA interacts with α-Fe2O3 to form an unstable surface complex. Subsequent to this complex formation, EDTA ions are released into the solution at high temperature leaving zirconium oxide on the surface of α-Fe2O3. This leads to the formation of interfacial states of Fe-O-Zr which provides the adhesion and initiates the nucleation of ZrO2. Formation of nano-crystalline ZrO2 particles on α-Fe2O3 has been seen by high resolution electron microscopy. It has been observed that islands of ZrO2 coalesced to form thick tetragonal ZrO2 coating on α-Fe2O3. Average size of ZrO2 crystallites is around 15nm and the coating thickness is around 0.25microns. The details of the mechanism of formation of interfacial states between ZrO2 and α-Fe2O3 have been explained by X-ray photoelectron spectroscopy and Raman analysis. Surface morphology and roughness have been studied by scanning electron microscopy and atomic force microscopy.