| Highly-sensitive Luminescence Thermometry of Sm2+ doped in Al2O3 Coatings Aleksandar Ćirić1; Zoran Ristic2; Zeljka Antic3; Ivana Zeković2; Stevan Stojadinović4; Mikhail G. Brik5; Miroslav Dramicanin2; 1VINčA INSTITUTE OF NUCLEAR SCIENCES, Knjaževac, Serbia and Montenegro; 2UNIVERSITY OF BELGRADE, VINCA INSTITUTE OF NUCLEAR SCIENCES, Belgrade, Serbia and Montenegro; 3VINCA INSTITUTE OF NUCLEAR SCIENCES, UNIVERSITY OF BELGRADE, Belgrade, Serbia and Montenegro; 4UNIVERSITY OF BELGRADE, FACULTY OF PHYSICS, Belgrade, Serbia and Montenegro; 5INSTITUTE OF PHYSICS, UNIVERSITY OF TARTU,, Tartu 50411, Estonia; PAPER: 64/SolidStateChemistry/Regular (Oral) SCHEDULED: 15:55/Tue. 29 Nov. 2022/Andaman 1 ABSTRACT: <p><strong>Summary </strong> γ-Al-2O3:Sm<sup>2+</sup> coatings were synthesized by the plasma electrolytic oxidation (PEO). The emissions originate from 4f<sup>5</sup>5d<sup>1</sup>→4f<sup>6</sup> and 4f<sup>6</sup>→4f<sup>6</sup> transitions of Sm<sup>2+</sup>. The emission spectra, recorded from 300 K to 673 K, reveled the rapid diminution of the <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>J</sub> transitions with increasing temperature. The 5d→4f broad-band emission increases in intensity up to 225 °C. The high-luminescence intensities and opposite intensity vs temperature trends of these emissions are an indication of the high sensitivities and low temperature resolution. The luminescence intensity ratio (LIR) are well-fitted to the Boltzmann distribution and the energy-crossover model with relative sensitivities: 3.5 %K-1 @ 300 K and 1.5 %K-1 @ 540 K. <strong>Introduction</strong> Sm2+ has a wide excitation band [1]. The emission spectrum of Sm<sup>2+</sup> features a broad-band due to 5d-4f transition and a series of sharp peaks due to 4f-4f transitions. The discovery of Al<sub>2</sub>O<sub>3</sub>:Sm<sup>2+</sup> [1] provided an opportunity for the investigation of this material as temperature sensor. The indications of its high potential for the phosphor thermometry were the existence of both the 5d-4f and 4f-4f emissions, high emission intensities, wide choice of excitation wavelengths, and the sole importance of the substrate material itself. The significant overlap of 5d with <sup>5</sup>D<sub>0</sub> level is an indication of the highly efficient f-f transitions [2]. The complete thermometric analysis was carried out. <strong>Methods</strong> 99.9% pure aluminium, 6061 and 7075 aluminium alloys were used as anode during the PEO. XRD was used for investigation of the coating crystallinity. High-stability 473 nm laser was used as an excitation source. The beams were transferred via a fiber-optic bundle. Emission spectra were recorded by the high-resolution spectrograph. The samples were placed on the liquid nitrogen cooled hot/cold stage. <strong>Results</strong> Emission spectra for LIR and LT were recorded from 100 K to 673 K. The <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>J</sub> emissions rapidly drop with increasing temperature, while the 4f-5d increases up to 225 °C. LIR is estimated from the ratio of 5d-4f and 4f-4f transitions, giving the excellent relative sensitivity values. Luminescence lifetime of <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>0</sub> is fitted to the energy crossover model [3], with maximum relative sensitivity 1.5 %K-1 @ 540 K. <strong>Conclusions</strong> A steady-state and time-resolved thermometry on a wide temperature range was carried out on the highly luminescent phosphor incorporated in the coatings of possibly the most important industrial material. LIR following Boltzmann distribution showed sensitivity among the highest ever recorded. The lifetime rapidly drops with increasing temperature.</p> References: <p>[1] S. Stojadinović, N. Tadić, R. Vasilić, Photoluminescence of Sm2+ / Sm3+ doped Al2O3 coatings formed by plasma electrolytic oxidation of aluminum, J. Lumin. 192 (2017) 110–116. https://doi.org/10.1016/j.jlumin.2017.06.043. [2] M. Tanaka, T. Kushida, Interference between Judd-Ofelt and Wybourne-Downer mechanisms in the 5D0-7FJ (J=2,4) transitions of Sm2+ in solids, Phys. Rev. B. 53 (1996) 588–593. https://doi.org/10.1103/PhysRevB.53.588. [3] M. Sekulić, Z. Ristić, B. Milićević, Ž. Antić, V. Đorđević, M.D. Dramićanin, Li1.8Na0.2TiO3:Mn4+: The highly sensitive probe for the low-temperature lifetime-based luminescence thermometry, Opt. Commun. 452 (2019) 342–346. https://doi.org/10.1016/j.optcom.2019.07.056.</p> |
