Er3+ -doped ZnO nanocrystalline powders are successfully prepared by the chemical precipitation method, using various doping concentrations of Er3+ at different annealing temperatures from 500°C to 900°C. The characteristic emission peaks of the excitation state 4S3/2 (550 nm), 2 H 11/2 (520 nm), 4 F 5/2 (455 nm) → 4 I 15/2 transition of Er3+ ions are observed in a wide visible band of the ZnO host. The relationship between the PL intensity of integration of nanocrystalline ZnO:Er3+ and the annealing temperature and doping concentration of Er3+ is given; it is found that the optimal dopant concentration and annealing temperature are 4.0 × 10-3 M and 850°C for the 4 S 3/2 → 4 I 15/2 (550 nm) and 4 F 5/2 → 4 I 15/2 (455 nm) transition of Er3+ . Based on these results, the mechanism of the emission spectra of ZnO is analyzed and its defects on the spectral properties are discussed. An energy transfer from excited states of ZnO hosts to doping Er3+ ion centers is revealed by the fact that PL intensity of the peaks of nanocrystalline ZnO:Er3+ changes with the annealing temperature and doping concentration of Er3+ , and another from the 4f–4f transition of Er3+ .
Optimizing thermocouple’s ZT through design innovation
