Band gap energy in nanocrystalline ZrO2:16%Y thin films

Abstract

The results of optical absorption measurements on nanocrystalline ZrO2:16%Y thin films are presented. Dense 0.7 μm thick films with 1–300 nm grain size have been obtained on sapphire substrate using a polymeric precursor spin coating technique. The relationship between the energy gap and microstructure of ZrO2:16%Y has been determined and discussed. The quantum confinement effect was observed at the grain size lower than 100 nm with the band gap energy shift of 0.25 eV when the microstructure was changed up to 1 nm. Some limitation of the model has been observed and discussed. The band gap energy of 5.62±0.05 eV has been determined as microstructure independent value.

Microstructure — Property relationships in nanocrystalline oxide thin films

“…As can be seen, the specimens with the smaller grain size are characterized by the highest amount of strain with the strain approaching that observed for polycrystaUine bulk YSZ as the grain size increases to larger than 100 nm. This observation correlated well with the optical spectroscopy data, which indicated size-dependent properties for the grain size below 100 nm [12,14,15]. In addition to the annealing temperature it has been found that the microstructure of the thin films is also related to the substrate.…”

“…The monotonic increase of the band gap energy with decrease in the grain size clearly shows the presence of the quantum confinement effect [12,14,29].…”

“…The YSZ and CeO 2 thin films were studied by optical spectroscopy to determine the relationship between the band energy and the microstructure [12,14]. The band gap energy (Eg) has been determined from the analysis of the absorption spectra.…”

“…Another advantage related to low processing temperatures is the ability to minimize interdiffusion between the film and substrate or between films with different compositions. The polymeric precursor spin coating technique has recently been used for the preparation of nanocrystalline oxides with the fluorite structure -CeOa [11,12], ZrO2:Y [10,[13][14][15], as well as more complex compounds SrCeO3:Yb [16], and…”

Unusual calcination temperature dependent tetragonal–monoclinic transitions in rare earth-doped zirconia nanocrystals

“…[3][4][5][6][7][8][9] Zirconia (especially in tetragonal or cubic phase) is technologically important in the engineering of advanced materials for its applications in catalysis, 10,11 transformation-toughened materials, 12 solid oxide fuel cells (SOFCs), 13,14 oxygen sensors, 15 and optics. 16 For example, t-ZrO 2 is the most effective catalyst among many oxides (including MgO, TiO 2 , ZnO, g-Al 2 O 3 , and Y 2 O 3 /Al 2 O 3 ) used in the hydrogenation of aromatic carboxylic acid to the corresponding aldehydes, 10 as well as in the isomerization of alkanes.…”