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• Er3+/Yb3+:GdNbO 4 micron-sized phosphor was synthesized by solid-state method. • Er3+ and Yb3+ concentrations have apparent effects on grain morphology. • The phosphor shows strong UCL, good thermal stability and adequate sensitivity. • The phosphor shows good chemical stability in high salinity environment. • The phosphor is promising for both thermometry and maritime protection. Micron-sized GdNbO 4 :Er3+/Yb3+ phosphors were prepared by employing a high-temperature solid-state reaction. The crystalline phase, morphology, composition, spectroscopic properties, and impact of rare-earth ion concentration, temperature and high salinity environment were systematically characterized. The extracted results show that phosphor is dominated by the existence of the GdNbO 4 crystalline phase. Their morphology and agglomeration phenomenon are strongly dependent on the rare-earth concentration. The phosphor exhibits also excellent up-conversion luminescence (UCL) properties under 980 nm excitation, while a two-photon process accounts for UCL. The following optimal concentrations were selected for enhanced UCL intensity: 10 mol% for Yb3+ and 3 mol% for Er3+. The phosphor shows excellent thermometric performances including strong UCL, good thermal stability, appropriate sensitivity and a wide sensitivity response range. To evaluate the accuracy of the present optical thermometer, the temperature of a heated bench has been comparatively measured by using the proposed optical thermometer and a commercial thermocouple with an accuracy of 1 K. By comparing the temperature values measured by the two methods, it can be concluded that the present optical thermometer has an accuracy better than 1.6 K. In addition, the phosphor exhibits good chemical stability in high salinity environment. Interestingly, its crystalline phase, structure, and UCL spectral structure, intensity and color are all preserved after one-month immersion into a high salinity solution. [Display omitted] GdNbO 4 :Er3+/Yb3+ phosphor was prepared by high-temperature solid-state method. Crystalline phase, morphology, composition, spectroscopic properties, and effects of rare-earth concentration, temperature and high salinity environment were fully characterized. The results show that the phosphor is promising for dual-application in thermometry and safety marks for maritime protection. [ABSTRACT FROM AUTHOR]

We exemplify the Er(NbO 3 ) 3 phosphor to demonstrate that the performance of the temperature sensor based on thermal effect of fluorescence intensity ratio (FIR) of 980-nm-upconverted Er 3+ green 530 and 550 nm emissions can be improved by using KBr-diluted phosphor. The sensing performance of the diluted phosphor plate was studied as a function of KBr:Er(NbO 3 ) 3 molar ratio from 0:1 to 100:1. The results show that the KBr dilution enables to enhance the fluorescence intensity and increase the temperature sensitivity. Meanwhile, the KBr itself does not affect either the Er 3+ spectroscopic properties or the FIR value. There is an optimum KBr: Er(NbO 3 ) 3 molar ratio within 15:1 and 20:1, for which the 530 (550) nm signal increases by 30% (20%) and the relative sensitivity at the physiological temperature increases by 14%. [ABSTRACT FROM AUTHOR]

Judd-Ofelt analysis was done for Er3+-doped NaLa(WO 4) 2 µm-sized phosphor using a method based on measured diffuse reflection spectrum and Er3+ 1.5 μm fluorescence lifetime. Judd-Ofelt intensity parameters, radiative rate, fluorescent branch ratio and radiative lifetime of some transitions of Er3+ ions in the phosphor have been obtained. • Er3+-doped NaLa(WO 4) 2 phosphor was synthesized by solid-state chemical reaction. • Its diffuse reflection spectrum and Er3+ 1.5 μm emission lifetime were measured. • Judd-Ofelt analysis was done on the basis of the measured spectrum and lifetime. • Radiative rate, fluorescent branch ratio and radiative lifetime were obtained. • The phosphor is promising for use in ratiometric fluorescence thermometry. Er3+-doped NaLa(WO 4) 2 is a promising phosphor material for applications in many fields including the ratiometric thermometry based on thermal effect of fluorescence intensity ratio (FIR) of green fluorescence of Er3+, which is directly correlated with Judd-Ofelt parameters Ω i (i = 2, 4, 6). Present paper reports synthesis and Judd-Ofelt spectroscopic properties of Er3+-doped NaLa(WO 4) 2 µm-sized phosphor. The phosphor was synthesized by solid-state chemical reaction and characterized by X-ray diffraction and Raman scattering techniques. The results show that the phosphor is dominated by NaLa(WO 4) 2 crystalline phase and has a maximum phonon energy 927 cm−1. Judd-Ofelt analysis was done for the phosphor using a safe, reliable method based on diffuse reflection spectrum and Er3+ 1.5 μm fluorescence lifetime. First, diffuse reflection spectrum of the phosphor was measured and relative absorption spectrum was calibrated from it using Kubelka-Munk theory. Second, Er3+ 1.5 μm fluorescence lifetime of the phosphor was measured and absorption cross-section spectrum was obtained based on the assumption that the 1.5 μm emission has 100% quantum efficiency. Finally, based on the absorption cross-section spectrum, standard Judd-Ofelt analysis was carried out to extract the Ω i. Radiative rate, fluorescent branch ratio and radiative lifetime of some transitions have been obtained from the known Ω i values. In addition, FIR proportional factor was evaluated in terms of Ω i and compared with those values of other materials. The result shows that the phosphor has a better prospect for the application in ratiometric thermometry. [ABSTRACT FROM AUTHOR]

We demonstrate the applicability of a ratiometric luminescence thermometer to microelectronic components. The thermometer, which consists of a 980 nm laser diode, two optical filters, two photocells and two multimeters, works on the basis of thermal effect on luminescence intensity ratio of 980-nm-upconverted 530 and 550 nm emissions of micron-sized Er3+/Yb3+-codoped NaGd(WO 4) 2 crystalline phosphor. The applicability is demonstrated by using it to monitor in realtime the temperature of an integrated circuit chip on a printed circuit panel (PCB) in operation. In parallel, the temperature was also measured independently using an infrared thermometer. A comparison shows that the temperature measured by the luminescence thermometer can be considered as identical to that measured by the infrared one within error. The consistency of the result from the luminescence thermometer with that from the infrared one, together with previously reported result that the NaGd(WO 4) 2 phosphor is an excellent insulator with a resistivity of 2.0 × 1011 Ω · m at 330 K, verifies the applicability of the luminescence thermometer to microelectronics, and the thermometer has a measurement error of 2 K. • Ratiometric fluorescence thermometer is applied to microelectronic components. • Er/Yb:NaGd(WO 4) 2 phosphor adopted has a high resistivity of 6.0 × 1012 Ω · m at 328 K. • The thermometer is used to monitor temperature of an integrated circuit on a PCB. • Results measured by fluorescence and infrared thermometers are thought as same. • The agreement of results verifies applicability and the measurement error is 2 K. [ABSTRACT FROM AUTHOR]

Dispersion relation is established for Er(NbO 3) 3 phosphor, which is an excellent candidate for optical thermometry based on thermal effect of Er3+ fluorescence intensity ratio. To achieve it, Er(NbO 3) 3 phosphor was dispersed into α-bromonaphthalene liquid to form a suspension. Then, refractive index values of the suspension were measured at wavelengths 473, 589.3, 632.8, 980, 1311 and 1553 nm by dropping it onto a plastic sheet. Subsequently, refractive indices of the Er(NbO 3) 3 phosphor were evaluated from these measured index values using Maxwell-Garnett relation. Finally, based on these Er(NbO 3) 3 index values, which have an error 0.03, a three-oscillator Sellmeier equation that considers contributions from Nb–O group, plasmons in far UV regime and phonons in infrared region is established. In parallel, a Cauchy dispersion equation is also established. Both equations can well fit the experimental data and the refractive indices predicted by the two equations can be regarded as identical within the error 0.03. Refractive indices of Er(NbO 3) 3 phosphor at different wavelengths ranging from 473 to 1553 nm have been obtained from the index values measured from an α-bromonaphthalene mixture suspended with Er(NbO 3) 3 phosphor grains. A three-oscillator Sellmeier equation n2(λ) = B UV - B IR λ2 + B 3 /(λ 3 −2-λ−2) is proposed that considers the contributions from plasmons in far UV, phonons in infrared region and the Nb–O group. A Cauchy dispersion equation n(λ) = A + B/λ2 + C/λ4 + D/λ6 is also attempted to fit the experimental data. The fitting results show that both equations can give accurate prediction of the refractive index value of the Er(NbO 3) 3 phosphor and have an accuracy better than 0.03 satisfying the demand for Judd-Ofelt spectroscopic analysis. Image 1 • Refractive indices of Er(NbO 3) 3 powder were measured at different wavelengths. • A three-oscillator Sellmeier equation n2(λ) = B UV -B IR λ2+B 3 /(λ 3 −2-λ−2) is suggested. • A Cauchy dispersion equation n(λ) = A + B/λ2+C/λ4+D/λ6 is also established. • Both equations give accurate prediction of refractive index value of Er(NbO 3) 3. • Both equations have an accuracy 0.03 satisfying demand for Judd-Ofelt analysis. [ABSTRACT FROM AUTHOR]

An application manner of Judd-Ofelt (J-O) theory to a luminescent powder is studied by exemplifying an Er3+-doped Li 5 La 3 Nb 2 O 12 nanophosphor, on which J-O analysis has been performed previously using the approach based on measured relative absorption (optical density) spectrum and Er3+ 1.5 μm fluorescence lifetime. Present study focuses on two key issues that are closely related to the reliability and application manner of the approach but not clarified in the previous study. First, whether or not a strong or medium-intensity oscillator, such as the 4I 15/2 ↔4I 13/2 (1.5 μm) one, can be excluded from the J-O least-square fit. Second, whether the relative ratio between the J-O intensity parameters Ω i (i = 2, 4, 6) remains unchanged as the integrated optical densities (IODs) of all transitions change all together by a factor x. Our studies show that the strong or medium-intensity transition oscillator, such as the 4I 15/2 ↔4I 13/2 one, must be included in the J-O fit. The relative ratios between Ω i change remarkably with the collectively varying factor x of the IODs for smaller x values because of magnetic dipole contribution of the 1.5 μm oscillator. The change is undesired as it may result in the deviation of Ω i values, and hence restricts the application manner of the related approach. A more reliable application manner of the approach is proposed. • Ω i are determined mainly by strong and medium-intensity transitions. • 1.5 μm transition affects Ω 4 and Ω 6 strongly, it must be included in J-O fit. • Ω i shows a linear relationship to integrated absorption cross-section. • Ω 4 /Ω 2 and Ω 6 /Ω 2 change remarkably with the relative absorption cross-section. • A more convincing and reliable method for calibration of Ω i has been suggested. [ABSTRACT FROM AUTHOR]