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Visible and near infrared absorption and emission (488 nm excitation) characteristics of ErNbO4 powder, which were prepared by calcining the Er2O3 (50 mol%) and Nb2O5 (50 mol%) powder mixture at 1100 and 1600 °C for different durations, have been investigated at room temperature. The absorption and emission characteristics of these calcined ErNbO4 powder were summarized and discussed in comparison with those of Er2O3. Weak emission of Er2O3 relative to the calcined ErNbO4 is mainly conducted with absorption difference at the excitation wavelength 488 nm. The obvious spectral changes from Er2O3 to calcined ErNbO4 samples are related to an elevated-temperature-assisted phase transformation according to the solid-state chemical reaction equation: Er2O3 + Nb2O5 ⇌ 2ErNbO4, which results in the changes of the ion environment of Er3+ and hence changes of the Stark levels of Er3+. The further spectral change as the strengthened calcination results from the improvement of ErNbO4 purity in the calcined mixture. The borders between two green transitions and between two near infrared transitions in the emission spectra of both calcined samples and Er2O3 were tentatively identified by referencing earlier reported emission spectra of the precipitated Z-cut VTE Er(2.0 mol%):LiNbO3 crystal and the match relation between absorption and emission spectra of the ErNbO4 powder. A comparison was performed on the spectra of calcined ErNbO4 powder and those of VTE Er(2.0 mol%):LiNbO3 crystals. The results allow to preliminarily deem the contribution of ErNbO4 precipitates, generated inside these crystals by the VTE procedure, to the spectra of these crystals. [Copyright &y& Elsevier]

Dependences of two factors on Judd-Ofelt (JO) intensity parameters Ω t (t = 2,4,6) have been studied theoretically by exemplifying the widely studied Er3+ ion, which is doped into Gd 3 Ga 5 O 12 , LiNbO 3 and SrGdGa 3 O 7 bulk single-crystals and β-NaYF 4 powder. The two factors include 1) selection of induced electric-dipole transitions for JO calculation and 2) integrated absorption coefficient (IAC) or integrated absorption cross-section (IACS) of individual electric-dipole transition of Er3+. Absolute and relative root-mean-square methods were considered in the JO fits and consistent results were obtained. Ω t depends mainly on strong and medium-intensity transitions. These transitions must be all included in the fit. The exclusion of an individual transition from the fit leads to deviation of Ω t. From the matrix elements [ U (t)]2 values, it is possible to rate how the inclusion or not of a transition affects the Ω t. The study also shows that the Ω t changes almost linearly with the IAC or IACS of an individual transition, and the relevant linear slope may have a positive or negative sign, depending on the [ U (t)]2 value. Moreover, the larger the [ U (t)]2 value is, the larger the corresponding Ω t value is. In addition, the Ω 2 , Ω 4 and Ω 6 are dependent of each other because it is the summation ∑ t Ω t [ U (t) ] 2 instead of its component term Ω t [ U (t) ] 2 that has a linear relationship to the IAC or IACS. [ABSTRACT FROM AUTHOR]

Dependences of Judd-Ofelt (JO) intensity parameters Ω t (t = 2,4,6) and their relative ratios (Ω 4 /Ω 2 and Ω 6 /Ω 2) on overall changing factor (q) of integrated absorption bands of Er3+ have been studied theoretically. These dependences can help us to use relevant method to correctly extract Ω t of a powder material. The study was done by exemplifying the widely studied Er3+ system, which is doped into Gd 3 Ga 5 O 12 , LiNbO 3 and SrGdGa 3 O 7 bulk single-crystals and β-NaYF 4 crystalline powder. The results show that the Ω t changes linearly with the overall changing factor q : Ω t = γ t q + ξ t. The linear feature changes from one material to another. The magnetic-dipole oscillator of the 1.5 μm transition results in non-zero nodal increment ξ t and hence dramatical changes of the relative ratios Ω 4 /Ω 2 and Ω 6 /Ω 2 (with q) in smaller q region. The dramatical feature limits application of the relevant method for Ω t calibration of a luminescent powder. To get the precise Ω t values using the relevant method, the q value must be large enough. This can be realized by adopting a thin powder plate with a low Er3+ concentration for spectral measurement. • Ω t is studied against overall varying factor q of all Er3+ absorption band areas. • Ω t has a linear relation to q and the linear feature relies on the host material. • Ω 4 /Ω 2 and Ω 6 /Ω 2 change dramatically with the q parameter in smaller q region. • The feature is caused by magnetic-dipole oscillator of the 1.5 μm transition. • The change concerns validity of related method for Ω t calibration of a phosphor. [ABSTRACT FROM AUTHOR]