Abstract
As a development on previous research on single crystals of Pr3+-doped yttria-stabilized zirconia (YSZ), we report here the preparation and optical properties of Yb/Pr co-doped YSZ single crystals with different Yb2O3 concentrations. Results from X-ray diffraction (XRD) and Raman spectroscopy indicated that all of the crystal samples had a cubic phase structure, and transmission was ≥88% in the 550–780 nm range. Photoluminescence (PL) under excitation with a 980 nm laser showed upconversion emission, and several peaks were observed centered on 448 nm, 508 nm, 525 nm, 542 nm, 617 nm and 656 nm. The effects of excited state absorption (ESA), energy transfer upconversion (ETU), cross relaxation (CR), and cooperative energy transfer (CET) on the upconversion luminescence and energy transition mechanism in YSZ crystals were further studied. The fluorescence lifetime of the 3P0 → 3H5 transition at 542 nm reached 207 μs, which shows that the samples are of potential use for laser and fluorescence output.
Highlights
Among the various hosts that have been used for the development of materials for luminescence, ZrO2 is favored for many applications because of its excellent thermal stability, chemical resistance, robust mechanical properties, and low phonon energy [1,2].pure ZrO2 can exist in three distinct structures, and transformation between these phases involves appreciable changes in volume, which frequently results in the formation of cracks when preparing crystals from melts [3,4,5]
Pure ZrO2 can exist in three distinct structures, and transformation between these phases involves appreciable changes in volume, which frequently results in the formation of cracks when preparing crystals from melts [3,4,5]
Cooling calcined samples of yttria-stabilized zirconia (YSZ) to room temperature, different crystal phases may be formed dependent on their Y2 O3 contents, but ZrO2 doped with 8 mol% Y2 O3 (8YSZ) has been found to be adequate for complete stabilization of the high-temperature cubic structure at room temperature [4,9,10], and to be a good matrix for doping with various rare earth ions that exhibit valuable luminescence properties [11]
Summary
Among the various hosts that have been used for the development of materials for luminescence, ZrO2 is favored for many applications because of its excellent thermal stability, chemical resistance, robust mechanical properties, and low phonon energy [1,2].pure ZrO2 can exist in three distinct structures, and transformation between these phases involves appreciable changes in volume, which frequently results in the formation of cracks when preparing crystals from melts [3,4,5]. Cooling calcined samples of yttria-stabilized zirconia (YSZ) to room temperature, different crystal phases may be formed dependent on their Y2 O3 contents, but ZrO2 doped with 8 mol% Y2 O3 (8YSZ) has been found to be adequate for complete stabilization of the high-temperature cubic structure at room temperature [4,9,10], and to be a good matrix for doping with various rare earth ions that exhibit valuable luminescence properties [11] These include upconversion (UC) luminescence, which corresponds to the emission of light of higher energy than that responsible for the excitation, and results from the consecutive absorption of two or more photons. The energy transfer modes vary between ions, and the different mechanisms for upconversion luminescence processes can be categorized as: excited state absorption (ESA), energy transfer upconversion (ETU), cooperative energy transfer (CET), photon avalanche (PA), and energy transfer medium upconversion (EMU) [14,15]
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