Structural evolution in reactive RF magnetron sputtered (Cr,Zr)2O3 coatings during annealing

Abstract

Reactive RF-magnetron sputtering is used to grow Cr 0.28 Zr 0.10 O 0.61 coatings at 500 °C. Coatings are annealed at 750°C, 810 °C, and 870 °C. The microstructure evolution of the pseudobinary oxide compound is characterized through high resolution state of the art HRSTEM and HREDX-maps, revealing the segregation of Cr and Zr on the nm scale. The asdeposited coating comprises α-(Cr,Zr) 2 O 3 solid solution with a Zr-rich (Zr,Cr)O x amorphous

Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)2O3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum

“…The most prominent coatings peaks, without substrate overlaps, appeared within d-spacing range of 2.5-4 Å and therefore chosen here from the total acquired 1-5.5 Å range. The short double dotted line, at a d-spacing of 2.7 Å, shows the RT position of the a-(104)-(Cr,Zr) 2 O 3 solid solution peak, as determined in previous work [43]. Here, it is shifted to a slightly larger d-spacing due to thermal expansion of the coating at 500°C.…”

“…In contrast to the as-grown amorphous coatings in this material system, a-phase (Cr,Zr) 2 O 3 solid solution coatings were grown at 500°C by Spitz et al [40]. The thermal stability and microstructural changes of this pseudo-binary oxide system were investigated by vacuum annealing at three different temperatures, 750, 810, and 870°C, in our previous work [43]. The study showed a slight increase in hardness on formation of t-ZrO 2 with dissolved Cr after annealing to 810°C, but the coating decomposed into t-ZrO 2 and bcc-Cr on loss of oxygen after annealing to 890°C.…”

“…Therefore, the aim of the present study was to determine the thermal stability and phase evolution of the Cr-rich, Cr 0.28 Zr 0.10 O 0.61 , coating from earlier work [43] both in vacuum and in air atmosphere and at higher maximum annealing temperature. The phase evolution during annealing was monitored continuously through in situ XRD at the synchrotron facility, DESY in Hamburg.…”

“…Table I shows the chemical composition of the coatings in the as-deposited state and after annealing. The chemical composition of the as-deposited coating was measured in the previous study with electron probe microanalysis (EPMA) [43] and remeasured in the present work with the top-view energydispersive X-ray spectroscopy (EDX). Both methods show that the as-deposited coatings is Cr-rich (Cr,Zr) 2 O 3 , close to stoichiometric composition with respect to oxygen.…”

“…The compositional balance consist of C and N and traces of Ar based on reference EPMA measurement from Ref. 43. The standard deviations are ;0.5 at.% or below for Cr, Zr, and O.…”