Temperature Sensing Properties base on Up‐Conversion Luminescence for NaYF₄: Er³⁺, Yb³⁺ Phosphor

Abstract

EDTA was used as chelating agent to synthesize Er 3 + , Yb 3 + codoped NaYF 4 phosphor by hydrothermal process. The crystallographic structures were characterized by X-ray Diffraction (XRD). The morphologies were analyzed by field emission scanning electron microscopy (FE -SEM). It can be known that with the increase of the EDTA/Re 3 + , the crystalline phase of samples change from α phase to the β phase. The temperature-dependent up-conversion emission spectra of the samples have been tested by the 980 nm laser excitation. Temperature sensing properties of samples were studied based on the fluorescence intensity ratio for two thermally coupled levels 2 H 11/2 and 4 S 3/2 of Er 3 + . The results show that the optical temperature sensing sensitivity increased gradually along with the EDTA/Re 3 + increasing, no matter the samples are α phase or β phase. And the sensitivity maximum of α phase samples is 0.00419 K À 1 (at 486 K, EDTA/Re 3 + = 3), the sensitivity maximum of β phase samples is 0.00466 K À 1 (at 550 K, EDTA/Re 3 + = 8). But the relative sensitivity has nothing to do with the amount of EDTA, only related to the crystalline phase. The relative sensitivity maximum of α phase samples is about 0.0105 K À 1 (at 303 k), the maximum relative sensitivity of β phase samples is about 0.0120 K À 1 (at 303 k). So, temperature sensing properties of β phase are better than that of α phase.Experimental section introduces the steps of hydrothermal synthesis of Er 3 + Yb 3 + co-doped NaYF 4 phosphors; the instruments and parameters of measuring XRD, SEM, emission spectra and temperature control.

Optical temperature sensor based on upconversion luminescence of Er3+ doped GdTaO4 phosphors

“…Particularly, based on the measurement of temperature‐dependent UC luminescence intensity of two thermally coupled energy levels of trivalent rare earth (RE 3+ ) ions, the non‐contact optical temperature sensor by using the fluorescence intensity ratio (FIR) technique still keeps a research hotspot in recent years owing to its advantages of fast response, high sensitivity and resolution 8‐13 . Under consideration of UC luminescence and temperature sensing properties, the Er 3+ ion with a pair of thermally coupled energy levels ( 2 H 11/2 and 4 S 3/2 ) is often regarded as the one of the most important activator ions to obtain strong UC luminescence in visible range under excitation of IR radiation because of its abundant metastable energy levels and high luminescent quenching concentration; meanwhile, it is also desirable in developing optical temperature sensors 14‐17 …”

“…range under excitation of IR radiation because of its abundant metastable energy levels and high luminescent quenching concentration; meanwhile, it is also desirable in developing optical temperature sensors. [14][15][16][17] It is generally known that the host lattice decides the distance between activator ions, the bond distance of activator ligand, coordination number, and symmetry. Thus, the host material plays a key role for the optical temperature sensing performance because the crystalline structure of host has a significant effect on luminescence intensity/efficiency and thermal/concentration quenching.…”

Combinations of Superior Inorganic Phosphors for Level‐Tunable Information Hiding and Encoding

“…It is certainly proved that UCL materials with different crystal fields possess obvious discrepancy in emission colors. [ 112,113 ] More importantly, UCL properties may be predicted as the crystal structure of a host is confirmed, including its symmetry, coordination environment around dopants, defect, and so forth. A positive effect of local crystal field on the regulation of UCL colors is demonstrated by testing optical properties in the Mn 2+ doped LiYF 4 :Er 3+ /Yb 3+ UCNPs.…”

Fabrication and characterization of up-converting β-NaYF4:Er3+,Yb3+@NaYF4 core–shell nanoparticles for temperature sensing applications

“…Under the same experimental conditions, i.e. under 980 nm excitation and in a wide temperature range from 328 to 550 K, the β-NaYF 4 :Er 3+ ,Yb 3+ nanoparticles revealed significantly higher sensitivities of 0.42% K −1 and 0.466% K −1 at 328 K and 550 K 26 , respectively than α-phase counterpart 27 . This confirms the importance of conscious synthesis process for the intentional obtaining of highly temperature sensitive nanomaterials and explains the reason for using beta phase nanomaterials in our research.…”

“…[11][12][13][14][15][16][17][18] . In the case of the optical temperature sensing applications, researchers focused especially on the sodium yttrium fluoride nanoparticles doped or co-doped with rare earth ions (NaYF 4 :RE 3+ nanoparticles) [19][20][21][22][23][24] , among which the NaYF 4 :Er 3+ , Yb 3+ nanoparticles were regarded as one of the most efficient upconversion materials for temperature sensing due to their unique luminescence properties and the large energy gap between two thermally coupled 2 H 11/2 and 4 S 3/2 energy levels [25][26][27] . One of the most important parameter of temperature sensor is its relative sensitivity to temperature changes which verify its quality as well as range of their applications.…”