Optical thermometric properties in Tb3+ and Eu3+-coactivated dual-emissive fluorophosphate phosphors

Abstract

Lanthanide (Ln) coactivated phosphors have received considerable attention in temperature sensing. Accordingly, Ln/Ln co-doped dual-emitting phosphors have been proposed as a novel optical thermometry scheme as a result of selected dual emission peaks from different luminescent centers rather better than individual emission bands from a single luminescent center. Here, dual-emissive Tb3+-Eu3+ lanthanide coactivated Sr3GdNa(PO4)3F fluorophosphate phosphors have been exploited as a new type of optical thermometer via fluorescence intensity ratio (FIR) technique. The threefold energy transfer phenomenon from Gd3+ to both Tb3+ and Eu3+, along with from Tb3+ to Eu3+ have been corroborated in Sr3GdNa(PO4)3F host by the photoluminescence spectra. On account of different thermal responses between Tb3+ to Eu3+ and the energy transfer process of Tb3+ to Eu3+, the FIR of Tb3+ to Eu3+ in Sr3GdNa(PO4)3F phosphor displays good temperature sensing property in the temperature range from 303 K to 483 K. Moreover, the monitored main emission peaks of the Tb3+ (5D4–7F5 transition) at 545 nm and the Eu3+ (5D0–7F4 transition) at 700 nm respectively, being commendably separated to afford a superior signal detectability. The maximum relative sensitivity reaches as high as 0.16% K−1, revealing that this phosphor might have potential application as a thermometric material for optical thermometry.