Abstract
Inorganic luminescent materials that can be excited with NIR radiation and emit in the visible spectrum have recently gained much scientific interest. Such materials can be utilized as anti-counterfeiting pigments, luminescent thermometers, bio-imaging agents, etc. In this work, we report the synthesis and optical properties of K2Gd(PO4)(WO4):Ho3+ and K2Gd(PO4)(WO4):20%Yb3+,Ho3+ powders. The single-phase samples were prepared by the solid-state reaction method, and the Ho3+ concentration was changed from 0.5% to 10% with respect to Gd3+. It is interesting to note that under 450 nm excitation, no concentration quenching was observed in K2Gd(PO4)(WO4):Ho3+ (at least up to 10% Ho3+) samples. However, adding 20% Yb3+ has caused a gradual decrease in Ho3+ emission intensity with an increase in its concentration. It turned out that this phenomenon is caused by the increasing probability of Ho3+ → Yb3+ energy transfer when Ho3+ content increases. K2Gd(PO4)(WO4):20%Yb3+,0.5%Ho3+ sample showed exceptionally high up-conversion (UC) emission stability in the 77–500 K range. The UC emission intensity reached a maximum at ca. 350 K, and the intensity at 500 K was around four times stronger than the intensity at 77 K. Moreover, the red/green emission ratio gradually increased with increasing temperature, which could be used for temperature sensing purposes.
Funder
Research Council of Lithuania
Subject
General Materials Science
Cited by
2 articles.
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