Development of new Eu3+/Sm3+ co-doped CaWO4 and CaMoO4 phosphors for optical thermometry based on ratiometric approach
Justyna Czajka, Marcin Runowski, Christian Hernández‐Álvarez, Inocencio R. Martín, Agata Szczeszak
Abstract
The Eu 3+ /Sm 3+ -co-doped CaWO 4 and CaMoO 4 scheelite-type phosphors were successfully synthesized by high-temperature solid-phase method and were investigated in detail for their promising applications in luminescence thermometry. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were used to study the structure and morphology of the phosphors synthesized. The co-doped CaMO 4 (M = W, Mo): Eu 3+ /Sm 3+ phosphors showed characteristic emission peaks at 534, 594, 657 and 705 nm corresponding to the intra-configurational transitions of 5 D 1 → 7 F 1 , 5 D 0 → 7 F 2 , 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 of Eu 3+ ions, as well as other emissions at 564, 603 and 648 nm, which were ascribed to 4 G 5/2 → 6 H 5/2 , 4 G 5/2 → 6 H 7/2 , and 4 G 5/2 → 6 G 9/2 transitions of Sm 3+ , respectively. The temperature sensing properties of both phosphors were investigated based on different temperature evolution of several emission bands of Eu 3+ and Sm 3+ . Specifically, using the luminescence intensity ratio (LIR) technique, we found that monitoring evolution of the LIR parameter 652/617 nm for the CaMoO 4 :1%Eu 3+ /1%Sm 3+ the maximum relative sensitivity of 1.28% K −1 can be achieved in the cryogenic T-range (93 K). Whereas, utilizing the same LIR for the CaWO 4 :1%Eu 3+ /1%Sm 3+ results in slightly smaller sensitivity of 1.18% K −1 . The obtained results, indicate that the developed phosphors may work as effective, remote temperature sensors, having great application potential in optical thermometry.