resumo
The hydrothermal synthesis of the novel Na[LnSiO(4)] (Ln = Gd, Eu, Tb) disordered orthorhombic system is reported. At 100 K, and above, these materials are best described in the centrosymmetric orthorhombic Pnma space group. At lower temperatures (structure solved at 30 K) the unit cell changes to body-centered with Imma symmetry. The materials exhibit unique photophysical properties, arising from both, this phase transformation, and the disorder of the Ln(3+) ions, located at a site with D-2d point symmetry. Na[(Gd0.8Eu0.1Tb0.1)SiO4] is an unprecedented case of a luminescent ratiometric thermometer based on a very stable silicate matrix. Moreover, it is the first example of an optical thermometer whose performance (viz., excellent sensitivity at cryogenic temperatures <100 K) is determined mainly by a structural transition, opening up new opportunities for designing such devices.
palavras-chave
X-RAY PHOSPHORS; LIQUID-CRYSTALS; TB-III; EU-III; TEMPERATURE; NANOTHERMOMETERS; NANOPARTICLES; NANOCRYSTALS; LUMINESCENCE; AMPLIFIERS
categoria
Chemistry
autores
Ananias, D; Paz, FAA; Yufit, DS; Carlos, LD; Rocha, J
nossos autores
Duarte Ananias
Investigador Auxiliar
Filipe Alexandre Almeida Paz
Investigador Principal
João Rocha
Prof. Catedrático
Luís Carlos
Professor Catedráticoagradecimentos
This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. D.A. acknowledges FCT for Postdoc Grant SFRH/BPD/95032/2013.