Optical thermometry and heating based on the upconversion fluorescence from Yb 3+ /Er 3+ co-doped NaLa(MoO 4 ) 2 phospho
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Zhijian Wu State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
Jung Hyun Jeongb) Department of Physics, Pukyong National University, Busan 608-737, South Korea (Received 10 July 2016; accepted 16 September 2016)
The NaLa(MoO4)2:Yb31/Er31 phosphor is synthesized through hydrothermal method with the further calcinations. The intense green upconversion (UC) emission is observed when it is excited by 980 nm pump power. Then we investigate the mechanism of UC emission based on the power dependent upconversion luminescence (UCL) spectra. Temperature sensing performance based on the Stark levels (2H11/2/ 4S3/2) of Er31 is estimated through investigating temperature-dependent UCL spectra from 298 K to 573 K. And the maximum value of sensor sensitivity based on FIR is approximately 0.00474 K1. Moreover, the variations of UCL intensities from 2H11/2/ 4S3/2 ! 4I15/2 transitions have been monitored with increasing pump power, which suggests that the pump energy can be absorbed by sample and heat it. In addition, the internal temperature of materials can be estimated by FIR technique. All the experimental results indicate that the phosphor has good potential in optical temperature sensing and optical heating.
I. INTRODUCTION
In recent years, people have paid more attention on lanthanide ion-doped phosphors for their application in remote temperature sensor and cell imaging, etc.,1–4 which the reason is that the exist of 4f n energy manifolds breaks the limit of the electric dipole selection rule. In addition, Yb31/Er31 co-doped NaLa (MoO4)2 phosphor have lower phonon energy, slimmer emission bands, and longer fluorescence lifetimes, compared to conventional luminescent materials, for example, organic fluorescent dyes.5–9 In particular, optical thermometry is widely used in internal temperature test and electrical power stations by using the FIR technology, in which the temperature-decided UCL spectra from thermally coupled energy levels (TCLs) of rare earth ions are contributed to it.10,11 The range of DE between TCLs is from 200 cm1 to 2000 cm1 and the quasiequilibrium is needed due to Boltzmann distribution.12 In addition, the energy difference between the 2H11/2 and 4 S3/2 levels of Er31 is approximately 800 cm1 according to previous publications, the result suggests that they have Contributing Editor: Winston V. Schoenfeld Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2016.377
the potential to regard as an optical temperature sensor by using FIR technique.13,14 The molybdate belongs to the sheelite-like (CaWO4) iso-structure, which shows great properties for broad range of application, such as catalysts, UC material, etc.15–18 Furthermore, the UC efficiency of molybdate is higher than traditional materials due to the lower lattice phonon energy.19–23 So the rare earth ionsdoped molybdate have ideal potential to act as an optical thermometer. The nea
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