title: Photoluminescent thermometer based on a phase-transition lanthanide silicate with unusual structural disorder.
abstract: The hydrothermal synthesis of the novel Na[LnSiO4] (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 D2d 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.
authors: Departments of Chemistry and ‡Physics, CICECO Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors: Duarte
authors: D
authors: Ananias
authors: Filipe A Almeida
authors: FA
authors: Paz
authors: Dmitry S
authors: DS
authors: Yufit
authors: Luís D
authors: LD
authors: Carlos
authors: João
authors: J
authors: Rocha