The initial steps of the reaction between ZnO and Al2O3 have been investigated with X-ray diffraction, atomic force microscopy, and X-ray absorption spectroscopy at the Zn-K edge starting from 45 nm thick zincite films deposited onto (110)- and (102)-oriented sapphire single crystals. The formation of nonequilibrium phase(s) has been detected for both orientations. For the (001)(zincite) parallel to (110)(sapphire) interface, the rate-determining step is the motion of the interface(s); the growth of the spinel layer is linear with time, with a rate constant k = 1.1(2) x 10(-9) cms(-1) at 1000 degrees C. At the (110)(zincite) parallel to (012)(sapphire) interface, the reaction shows dumped oscillations. The results are discussed along with a comparison with previous results on thinner films to clarify the role of interfacial free energy and crystallographic orientation.

Role of Interfacial Energy and Crystallographic Orientation on the Mechanism of the ZnO + Al2O3 -> ZnAl2O4 Solid-State Reaction: I. Reactivity of Films Deposited onto the Sapphire (110) and (012) Faces

SPINOLO, GIORGIO;ZEMA, MICHELE;TARANTINO, SERENA CHIARA;GHIGNA, PAOLO
2013-01-01

Abstract

The initial steps of the reaction between ZnO and Al2O3 have been investigated with X-ray diffraction, atomic force microscopy, and X-ray absorption spectroscopy at the Zn-K edge starting from 45 nm thick zincite films deposited onto (110)- and (102)-oriented sapphire single crystals. The formation of nonequilibrium phase(s) has been detected for both orientations. For the (001)(zincite) parallel to (110)(sapphire) interface, the rate-determining step is the motion of the interface(s); the growth of the spinel layer is linear with time, with a rate constant k = 1.1(2) x 10(-9) cms(-1) at 1000 degrees C. At the (110)(zincite) parallel to (012)(sapphire) interface, the reaction shows dumped oscillations. The results are discussed along with a comparison with previous results on thinner films to clarify the role of interfacial free energy and crystallographic orientation.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/856730
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