Enhanced up-conversion and temperature-sensing behaviour of Er³⁺ and Yb³⁺ co-doped Y₂Ti₂O₇ by incorporation of Li⁺ ions

Abstract

Y2Ti2O7:Er(3+)/Yb(3+) (EYYTO) phosphors co-doped with Li(+) ions were synthesized by a conventional solid-state ceramic method. X-ray diffraction studies show that all the Li(+) co-doped EYYTO samples are highly crystalline in nature with pyrochlore face centred cubic structure. X-ray photon spectroscopy studies reveal that the incorporation of Li(+) ions creates the defects and/or vacancies associated with the sample surface. The effect of Li(+) ions on the photoluminescence up-conversion intensity of EYYTO was studied in detail. The up-conversion study under ∼976 nm excitation for different concentrations of Li(+) ions showed that the green and red band intensities were significantly enhanced. The 2 at% Li(+) ion co-doped EYYTO samples showed nearly 15- and 8-fold enhancements in green and red band up-converted intensities compared to Li(+) ion free EYYTO. The process involved in the up-conversion emission was evaluated in detail by pump power dependence, the energy level diagram, and decay analysis. The incorporation of Li(+) ions modified the crystal field around the Er(3+) ions, thus improving the up-conversion intensity. To investigate the sensing application of the synthesized phosphor materials, temperature-sensing performance was evaluated using the fluorescence intensity ratio technique. Appreciable temperature sensitivity was obtained using the synthesized phosphor material, indicating its applicability as a high-temperature-sensing probe. The maximum sensitivity was found to be 0.0067 K(-1) at 363 K.

Yb3+/Er3+ co-doped CaMoO4: a promising green upconversion phosphor for optical temperature sensing

“…It is well known that the Er 3+ 2 H 11/2 ? 4 I 15/2 transition is hypersensitive [13], and the temperature sensitivity of the material varies remarkably for Er 3+ ions in different hosts [8][9][10][11][12][14][15][16][17][18][19]. Hence, searching a suitable Er 3+ /Yb 3+ host is of great significance in thermometry application.…”

Up-conversion luminescent properties and optical thermometry of LaMgAl11O19: Yb3+/Er3+ phosphors

“…FIR was based on the measurement of fluorescence intensities from two thermally coupled levels of one kind RE-ions, which was independent of spectrum losses and fluctuations in the excitation intensity. So it can provide more accurate temperature measurements [2][3][4]. For the RE ions with coupled levels, Er 3 þ has been investigated extensively due to its green UC emissions originating from two thermally coupled levels 2 H 11/2 and 4 S 3/2 .…”

Upconversion luminescence enhancement and temperature sensing behavior of F− co-doped Ba3Lu4O9:Er3+/Yb3+ phosphors

“…Just as discussed above, the incorporation of F À ions into the host matrix to occupy O 2À site or enter interstitial sites would modify the local crystal eld environment of Er 3+ ions, lower site symmetry of the lanthanide activator ions and break the 4f-4f forbidden transitions to enhance the UC luminescence. 16,26,[39][40][41] Secondly, the ux effect of BaF 2 could not be neglected and F À doping may also improve crystallinity and particle morphology of samples as discussed in the Fig. 4, which further enhances the UC luminescence.…”

“…25,26 Among these applications, the temperaturedependent uorescence lifetime and uorescence intensity ratio (FIR) are regarded as very promising techniques for optical temperature sensors. The FIR technique based on the measurement of luminescence intensities from two thermally coupled levels of RE 3+ ions is independent of signal losses and uctuation in the excitation intensity and has the potential to improve measurement accuracy and resolution signicantly.…”