Stabilization of tetragonal and cubic phases of ZrO2 in pulsed sputter deposited ZrO2/Al2O3 and ZrO2/Y2O3 nanolayered thin films

Barshilia, Harish C and Deepthi, B and Rajam, KS (2008) Stabilization of tetragonal and cubic phases of ZrO2 in pulsed sputter deposited ZrO2/Al2O3 and ZrO2/Y2O3 nanolayered thin films. Journal of Applied Physics, 104 (113532). ISSN 0021-8979

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Abstract

We have prepared nanolayered thin films of ZrO2 /Al2O3 and ZrO2 /Y2O3 using pulsed sputtering to study the feasibility of stabilization of various polymorphs of ZrO2. These films have been deposited at various substrate temperatures 350–700°C, individual layer thicknesses 1.9–25.2 nm, and modulation wavelengths 9.6–32.7 nm. The cross section of ZrO2 and Y2O3 films consisted of microcolumns, whereas the ZrO2 /Al2O3 and ZrO2 /Y2O3 multilayer systems exhibited a less columnar microstructure. X-ray diffraction XRD data showed monoclinic, cubic, and amorphous structures for ZrO2, Y2O3, and Al2O3 thin films, respectively. The tetragonal phase of ZrO2 t-ZrO2 was stabilized for ZrO2 /Al2O3 nanolayered thin films prepared at ��13.8 nm. Our studies demonstrated that a critical ZrO2 thickness 10.5 nm at a substrate temperature of 700°C is required in order to stabilize the t-ZrO2 phase, which was in agreement with thermodynamically derived critical radius for the stabilization of the tetragonal phase. In the case of ZrO2 /Y2O3 nanolayered thin films, the cubic phase of ZrO2 was stabilized for films prepared at 24.4 nm 9.9 nm. The nanolayered thin films prepared at =9.9 nm exhibited satellite reflections of third order, suggesting the formation of superlattice structure. The formation of various polymorphs of ZrO2 was also confirmed by micro-Raman spectroscopy. XRD studies of nanolayered thin films heat treated in air demonstrated the stability of the tetragonal and the cubic phases of ZrO2 in the ZrO2 /Al2O3 and ZrO2 /Y2O3 multilayers, respectively, up to 1100 °C. ZrO2 /Al2O3 and ZrO2 /Y2O3 nanolayered thin films exhibited maximum nanoindentation hardness values of 30.5 and 28 GPa, respectively, which were very high as compared to the rule-of-mixture values. Detailed studies on elastic/plastic behavior of the multilayers indicated highest resistance to plastic deformation for the ZrO2 /Al2O3 multilayers.

Item Type:	Article
Subjects:	CHEMISTRY AND MATERIALS > Chemistry and Materials (General) PHYSICS > Solid-State Physics
Depositing User:	Mr N Selvakumar
Date Deposited:	02 Aug 2011 05:17
Last Modified:	02 Aug 2011 05:17
URI:	http://nal-ir.nal.res.in/id/eprint/9745

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