The comparison of Pr³⁺:LaF<inf>3</inf> and Pr³⁺:LiYF<inf>4</inf> luminescent nano- and microthermometer performances

Abstract

© 2019, Springer Nature B.V. In the present work, we make a comparison of Pr3+:LaF3 and Pr3+:LiYF4 luminescent nano- and microthermometer performances. We studied Pr3+:LaF3 nanoparticles, synthesized via co-precipitation method (further Pr3+:LaF3 (co-precipitation)), Pr3+:LaF3 nanoparticles, synthesized via hydrothermal method (further Pr3+:LaF3 (hydrothermal)), and Pr3+:LaF3 microparticles as well as Pr3+:LiYF4 nanoparticles, synthesized via hydrothermal method (further Pr3+:LiYF4 nanoparticles) and Pr3+:LaF3 microparticles. According to the X-ray diffraction, Pr3+:LaF3 (co-precipitation) and Pr3+:LaF3 (hydrothermal) nanoparticles are hexagonal-structured nanocrystals. Pr3+:LiYF4 nanoparticles are tetragonal-structured nanocrystals. The average diameters of Pr3+:LaF3 (co-precipitation), Pr3+:LaF3 (hydrothermal), and Pr3+:LiYF4 nanoparticles are 13.9, 19.4, and 33.3 nm, respectively. The Pr3+:LaF3 (co-precipitation) and Pr3+:LaF3 (hydrothermal) nanoparticles demonstrate broadband luminescence caused by crystal lattice defects (luminescence background). This luminescence background notably decreases the temperature sensitivity of these samples. The luminescent background removing procedure significantly complicates the signal processing procedure. Pr3+:LaF3 microparticles, Pr3+:LiYF4 nanoparticles, and Pr3+:LaF3 microparticles do not demonstrate this undesirable phenomenon. The absolute temperature sensitivity Sa of Pr3+:LiYF4 nanoparticles, Pr3+:LiYF4 microparticles, and Pr3+:LaF3 microparticles at 300 K are 0.0117 ± 0.0010, 0.0106 ± 0.0010, and 0.0102 ± 0.0012 K−1, respectively. Although the values of Sa are very close for these samples, the nanosized dimensionality of Pr3+:LiYF4 nanoparticles allows achieving high spatial resolution and expanding the fields of application of Pr3+:LiYF4 nanoparticles.