Strong sensitivity enhancement in lifetime-based luminescence thermometry by co-doping of SrTiO3:Mn4+ nanocrystals with trivalent lanthanide ions

Abstract

The co-doping of SrTiO₃:Mn⁴⁺ luminescent nanocrystals with trivalent lanthanide ions (Ln³⁺ = Lu³⁺, Tm³⁺, Er³⁺, Ho³⁺, Dy³⁺, Eu³⁺, and La³⁺) is demonstrated as a new strategy for significant sensitivity improvement of lifetime-based luminescent thermometers. SrTiO₃:Mn⁴⁺:Ln³⁺ nanocrystals of about 25 nm diameter were prepared by the modified Pechini method and characterized using X-ray powder diffraction and electron microscopy techniques. The temperature dependence of Mn⁴⁺ emission in SrTiO₃ was considerably altered by the co-doping of Ln³⁺ due to the cooperating effects of Mn⁴⁺ → Ti³⁺ and Mn⁴⁺ → Ln³⁺ energy transfers. A substantial enhancement of the relative sensitivity of lifetime-based thermometry as high as 145% with respect to the unco-doped nanocrystals reveals the success of the approach. The obtained values of maximal relative sensitivity for different Ln³⁺ co-dopants are 5.10% K⁻¹ at 290 K for Er³⁺, 5.00% K⁻¹ at 301 K for Eu³⁺, 4.84% K⁻¹ at 303 K for Dy³⁺, 4.71% K⁻¹ at 289 K for Ho³⁺, and 3.87% K⁻¹ at 290.7 K for Lu³⁺.