The influence of grain size and vanadium concentration on the spectroscopic properties of YAG:V3+,V5+ and YAG: V, Ln3+(Ln3+ = Eu3+, Dy3+, Nd3+) nanocrystalline luminescent thermometers

The first demonstration of using V-based phosphor as a luminescent temperature sensor is presented. The luminescent properties of YAG:V3+, V5+ and YAG:V Ln(3+)(Ln(3+)=Eu3+, Nd3+ and Dy3+) nanocrystals were investigated in a wide range of temperature (-150 degrees C-300 degrees C). The influence of dopant concentration and size of the nanocrystals on the emission color output of the YAG:V3+, V5+ was analyzed. The provided analysis reveals that V3+ and V5+ are mainly localized in octahedral sites of Al3+ of core part of the nanocrystals and surface tetrahedral sites of Al3+, respectively. The emission spectra consists of two broad emission bands, attributed to the CT emission of V5+(at 520 nm) and T-3(2g) -> T-3(1g) electronic transition emission of V3+(at 820 nm). It was found that emission color output of the YAG:V3(+,) V5+ nanocrystals can be modulated either by the vanadium concentration or by the size of nanocrystals. Based on the V3+ to V5+ emission intensity ratio (LIR) in the temperature range from -150 degrees C to 300 degrees C self-reference thermometer was defined, which reveals 0.7%/degrees C of sensitivity at the physiological temperature and increases above 4% in 250-300 degrees C. However its usable temperature range was strongly restricted. It was showed that by the appropriate choice of lanthanide co-dopants, the temperature range in which high sensitivity can be modulated (0.4%/degrees C at 100 degrees C for YAG:V, Eu3+; 4%/degrees C at -150 degrees C for YAG:V, Dy3+; and 0.8%/degrees C at 300 degrees C for YAG:V, Nd3+). (c) 2018 Elsevier B.V. All rights reserved.