Synthesis of ZrO2:Pr3+,Gd3+ nanocrystals for optical thermometry with a thermal sensitivity above 2.32% K−1 over 270 K of sensing range

Abstract

Nowadays, there is enthusiastic effort to develop luminescent thermometers used for remote and high-sensitivity temperature readout over a wide sensing range. Herein, Pr³⁺ and Gd³⁺ co-doped ZrO₂ nanocrystals are designed, prepared and investigated by XRD, Raman spectroscopy, XPS, TEM, EDS, DRS, PLE and PL spectroscopy. Upon 275 nm irradiation, the PL spectrum of ZrO₂:Pr³⁺,Gd³⁺ is found to be composed of a narrow emission peak at 314 nm (Gd^{3+ 6}P_7/2–⁸S_7/2), a broad defect-related emission band at 400 nm, and several emission peaks in the wavelength region of 585–700 nm (Pr^{3+ 1}D₂–³H₄, ³P₀–³H₆, and ³P₀–³F₂), which exhibit different thermal responses owing to the effects of the various non-radiative relaxation processes and trap energy levels. Accordingly, the luminescence intensity ratio (LIR) between the Pr^{3+ 1}D₂–³H₄ and Gd^{3+ 6}P_7/2–⁸S_7/2 transitions demonstrates excellent relative sensing sensitivity values ((2.32 ± 0.01)% K⁻¹–(8.32 ± 0.05)% K⁻¹) and low temperature uncertainties (0.08 K–0.28 K) over a wide temperature sensing range of 303 K to 573 K, which are remarkably better than those of many other luminescence thermometers. What is discussed in the present study may be conducive to broadening the research region of RE³⁺ doped luminescence thermometric phosphors, especially for materials with rich 4f–4f transition lines and defect-related luminescence.