The fabrication of size-dependent
rare earth ion-doped materials
for photonic devices has attracted interest in the search for color
tunability and noncontact temperature sensing properties with high
sensitivity. Sol–gel Pechini is an appropriate method compared
to other methods to prepare Yb3+/Er3+:gadolinium
gallium garnet (GGG) crystals at the nanoscale. This work presents
a study of white-light emission and optical thermometry properties
of Yb3+/Er3+:GGG nanocrystals based on the upconversion
(UC) blue, green, and red emissions observed under 975 nm laser excitation.
The color coordinates of the studied nanocrystals were affected by
the crystalline size. Yb3+ (2 mol %)/Er3+(1
mol %):GGG nanocrystals have the highest maximum absolute sensitivities
of 0.0028 K–1 at 378 K and 0.0041 K–1 at 561 K for 17 and 45 nm crystalline sizes, respectively. In light
of the observations, Yb3+/Er3+:GGG may be a
good candidate material for use in white light and optical temperature
sensing.
Site-selective spectroscopy is a tool that can be used to uncover the presence of multiple sites available to optically active ions in host lattices. In this Article, we present techniques that can be applied to appraise the different sites that may occur in systems where charge compensation is required or in systems where such compensation is not present. We then consider some garnet crystals doped with chromium ions. For the Cr-doped garnets (YAG, GGG, GSGG, and CYMGG), we present luminescence and lifetime data over a wide temperature range, and infer not only the presence of different centers, but also the interaction among them as a function of temperature.
Phosphors of δ‐Y2Si2O7 doped with Nd3+ ions were prepared in the SiO2–Y2O3 binary systems using the solgel technique. Nano‐sized crystalline phosphor powders were obtained by annealing the dried gels at 1480°C. The average grain sizes of the NYS1, NYS2, NYS3, and NYS4, powders were estimated to be 44.1, 41.3, 48.1, and 53.2 nm from the grain size distribution curves, respectively, and these results were confirmed by transmission electron microscope measurements. The spectroscopic properties of the powders were studied by measuring the luminescence spectra, and the decay curves of the 4F3/2 emission level were measured at room temperature.
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