Quantum chemistry and QSPR study on relationship between crystal structure and emission wavelength of Eu2+‐doped phosphors

Abstract— The relationship between crystal structures and emission properties has been computationally investigated for Eu²⁺‐doped phosphors. The electronic structure of the Eu²⁺‐doped BaMgAl¹⁰O¹⁷ phosphor was analyzed by using the quantum chemistry method. The different effects of O and Ba atoms on the Eu 5d states were determined. The presence of O and Ba atoms increases and decreases the energy level of the Eu 5d orbital by forming anti‐bonding and bonding interactions, respectively. According to the electronic‐structure analysis, the structure index that represents the local geometrical information of the Eu atom was defined. The relationship between the crystal structures and the emission wavelengths of the 1 6 Eu²⁺‐doped oxide phosphors were studied by using the quantitative structure‐property relationship (QSPR). The QSPR model suggested that the both O and alkaline‐earth atoms around the Eu atom are of importance in the determination of the emission wavelength. The interaction between the Eu and the nearest O atoms make the Eu²⁺ emission wavelength short. On the other hand, the interaction from the alkaline‐earth atoms around the Eu atom lengthens the Eu²⁺emission wavelength. This evaluation method is useful in selecting the host material that indicates a desirable emission wavelength of the Eu²⁺‐doped phosphors.     

Orange‐red upconversion luminescence of Sm3+‐doped ZnO‐B2O3‐SiO2 glass by infrared femtosecond laser irradiation

Abstract— Near‐infrared‐to‐visible upconversion luminescence was observed in Sm³⁺‐doped ZnO‐B₂O₃‐SiO₂ glass under femtosecond laser irradiation. The luminescence spectra show that the upconversion luminescence originates from ⁴G^5/2 to ⁶H^j/2 (j = 5, 7, 9) transition of Sm³⁺. The dependence of the fluorescence intensity of Sm³⁺ on the pump power indicates that a two‐photon absorption process is dominant in the conversion of infrared radiation to the visible luminescence. The analysis of the upconversion mechanism reveals that the simultaneous absorption of two infrared photons produces the population of upper excited states, which leads to the characteristic orange‐red emission of Sm³⁺. A three‐dimensional display is demonstrated based on the multiphoton absorption upconversion luminescence.