Investigation Of Luminescence Properties Of Eu³⁺：GdalO₃，Eu³⁺：LaAlO₃and Er³⁺：Y₂O₃Powder

In the last few decades much attention has been paid to the research on rare-earthdoped upconversion luminescent materials owing to their application in varioustechnological fields. The energy levels of trivalent rare earth ion configuration isextremely rich spectrum from f-f transition within the4f shell has a unique spectralcharacteristics in the field of optical, electronic, magnetic, and other importantapplications. Doping the ion of rare earth to the different site select of crystal, therewill be a little difference in their energy level. Based on the measured spetra, we cananalyze the site select information of rare earth ion in the crystal if we stimulate theion by choosing appropriate stimulating wavelength.In the essay, we use site select of excitation spectrum to study fluorescent powderof GdAlO₃:Eu³⁺and LaAlO₃:Eu³⁺.Besides, we also pump the Y₂O₃: Er³⁺:by using1550nm infrared laser, and analyze the up-conversion mechanism of it.Eu³⁺-doped GdAlO₃and LaAlO₃phosphors prepared by sol-gel method havebeen investigated by the site-selective laser spectroscopy along with the decay timesunder a pulsed, tunable, and narrowband dye laser at room temperature. Theexcitation spectrum of the⁷F0â†'⁵D0transition of GdAlO₃: Eu³⁺was recorded bymonitoring the⁵D0â†'7F2emission at615.10nm. The⁷F0and⁵D0levels arenondegenerate and each transition between them has one peak per site. This is inagreement with the structure of GdAlO₃, where the doped-ion occupies only onecrystallographic site. The laser-selective excitation spectrum of LaAO3:Eu³⁺weremeasured by monitoring the⁵D0â†'7F2emission at616.20nm. It is well known that thedoped-Eu³⁺ions substitute for La3+ions which only occupy the D3position inhexagonal LaAlO₃, and the initial and final energy state involved in the⁷F0â†'⁵D0transition is nondegenerate, so only one site is expected. However, the excitationspectrum clearly showed three distinct.The different positions confirm the existenceof at least three sites over which the Eu³⁺dopant is distributed. The lifetimes are determined to be3.426and2.723ms for GdAlO₃:Eu³⁺and LaAlO₃:Eu³⁺samplesshown in Fig.3. The different lifetime values maybe due to the different energytransfer rates of Eu³⁺ions in the two kinds of host materials, which are affected by thedistance of doped-Eu³⁺ions and the matrix lattice field. Therefore, we are sure to getpure orthorhombic GdAlO₃by sol-gel method, but we can not ascertain that theexactly pure hexagonal LaAlO₃could be obtained through this way.Ultraviolet upconversion emissions were investigated in this paper. Ultravioletupconversion emissions around390nm were observed in Er³⁺:-doped oxide underdiode laser excitation of1550nm, complying the infrared to ultraviolet upconversionprocess. Pump power dependence investigations indicate that they arise fromthree-photon processes, which can be well explained by using the proposedupconversion mechanisms.