Co-substitution of Zn 2+ /Ge 4+ pair within garnet phosphors activated by Er 3+ for enhancing luminescence properties and optical thermometry

Abstract

Gadolinium gallium garnet has been emerging as a starlet for preparing efficient luminescent materials, while via crystal field engineering the luminescence properties of rare-earth activator in its solid solution phosphors were scarcely explored. In this work, Er 3+ -doped Gd 3 Zn x Ga 5-2x Ge x O 12 (GZG 5- 2x G:Er 3+ ) solid solutions were prepared by high-temperature solid-state reaction, where a hetero-valent co-substitution strategy was implemented via introducing Zn 2+ /Ge 4+ pair to replace 2 Ga 3+ sites. X-ray diffraction Rietveld refinements confirm all samples crystallized into pure garnet phase. Upon 381 nm excitation, Er 3+ concentration was spectrally optimized to be about 10%, substituting the Gd 3+ sites, and via the Zn 2+ /Ge 4+ co-substitution, luminescence intensity of GZG 2 G:10%Er 3+ increases by more than 3 times in comparison with that of the baseline GZGG:10%Er 3+ sample. All the GZG 5-2x G:10%Er 3+ solid solution samples color in bright green under illumination using an ultraviolet ~ 365 nm lamp.Thermometric properties of Er 3+ 2 H 11/2 -4 S 3/2 thermally coupled levels of were systematically studied on basis of fluorescence intensity ratio principle. The GZG 5-2x G:10%Er 3+ all can perform temperature sensing over a wide temperature range of 298-573 K with a maximum relative sensitivity (S r ) above 1.20% K -1 and an applicable minimum temperature resolution (δT) around 0.4 K. Continuous exploration of solid solution-manipulating luminescent properties would develop novel thermometry probes (particularly for activator with spin-allowed transitions) with higher S r and smaller δT for practical optical temperature sensing.