Blue- and white-emitting Dy3+-doped aluminum oxide prepared using precursor synthesis

Abstract

Al2O3:Dy3+ phosphors have been successfully prepared using the precursor method utilizing Al1-xDyx(OH)(HCOO)2 as a precursor. The synthesis of the precursor was carried out according to the reaction of the metal nitrates with different concentrations of formic acid. A similar method was used to obtain dysprosium formate, Dy(HCOO)3, which is the most probable impurity phase formed during the preparation of Al1-xDyx(OH)(HCOO)2. The crystal structures of Al1-xDyx(OH)(HCOO)2 and Dy(HCOO)3 have been studied using X-ray powder diffraction and Raman spectroscopy. The phosphors in the form of their amorphous oxides (Al2О3:Dy3+) and solid solutions ((Al1-xDyx)2O3) with a spinel γ-Al2О3 structure were obtained via the thermolysis of Al1-xDyx(OH)(HCOO)2 under a helium atmosphere. The absorption, excitation, and luminescence spectra of the phosphors prepared with different dopant concentrations and upon annealing the Al1-xDyx(OH)(HCOO)2 precursor at various temperatures were analyzed in detail. For both amorphous Al2О3:Dy3+ and (Al1-xDyx)2O3 phosphors, the luminescence intensity associated with intrinsic internal defects in the aluminum host decreases upon increasing the dysprosium content. The energy transfer from the host to the activator (Dy3+) leads to a shift in the luminescence in the white color region, which is confirmed by the CIE chromaticity coordinates of the (Al1-xDyx)2O3 compounds. The Al2О3:0.005Dy3+ and γ-(Al0.995Dy0.005)2O3 aluminum oxides exhibit high thermal stability over a wide temperature range and are promising blue-white luminescence materials.