Dy³⁺-Assisted Negative-Thermal Quenching in Ho³⁺-Doped SrMoO₄ for Luminescence Thermometry and Lighting Applications

Strategic Investigation of Dual-Mode Light Emission from Tm3+/Ho3+/Yb3+-Activated NaLa(MoO4)2 Phosphors for Color Tunability and Optical Temperature Sensing Applications

“…As shown in Figure b, these spectra exhibited evident emission characteristics that can be evidently attributed to the presence of Tm 3+ and Ho 3+ ions. Several significant transitions of the Ho 3+ ions were observed, namely, the transitions 5 S 2 , 3 F 4 → 5 I 8 at approximately 545 nm and 5 F 5 → 5 I 8 at 641 nm . Furthermore, it was observed that Tm 3+ ions emit light at wavelengths of 452, 467, 486, 655, and 681 nm, which can be attributed to electronic transitions 1 D 2 → 3 F 4 , 1 G 4(2) → 3 H 6 , 1 G 4(1) → 3 H 6 , 1 G 4 → 3 F 4 , and 3 F 2,3 → 3 H 6 , respectively .…”

“…The PLE and PL spectra of T9H3 were carefully obtained using 452 and 544 nm emissions and 358 nm excitation wavelengths, as presented in Figure a. The observed spectra clearly display the unique excitation lines associated with individual Tm 3+ and Ho 3+ ions, indicating the presence of spectral overlap . It is worth mentioning that a mutual spectral coincidence was observed at a wavelength of 358 nm, within the NUV range.…”

“…One of the essential classes of phosphors studied for thermometry is molybdates. Molybdates possess numerous advantages, such as superior thermal and chemical stability, low toxicity, and an easy synthesis route. − The NaLaMoO 4 (NLMO) double molybdate is proven to be an ideal host for Ln 3+ ions as the doped Ln 3+ ions can be incorporated into the matrix without the occurrence of any impurity phase, allowing excellent Ln 3+ emission properties . The scheelite-type structure of NLMO is assumed to be a stable host for Ln 3+ ions with low-concentration quenching.…”

“…The Yb 3+ ion has a large absorption cross-section for 980 nm NIR radiation and can transfer its energy to the excited levels of Tm 3+ ions, thereby yielding intense upconversion in blue and NIR regions. Another Ln 3+ ion that is widely used with Yb 3+ ion for the upconversion process is Ho 3+ . ,, The Ho 3+ ion gives emission from green to the NIR region through various optical processes, such as downconversion, upconversion, and quantum cutting . The upconversion process in Ho 3+ can be realized by the use of Yb 3+ as a sensitizer.…”