Constructing sensitive luminescent thermometers via energy transfer in Ce3+ and Eu2+ co-doped Ca8Mg3Al2Si7O28 phosphors

Abstract

In this study, Ce³⁺ and Eu²⁺ co-doped Ca₈Mg₃Al₂Si₇O₂₈ phosphors are designed and synthesized for applications in highly sensitive optical thermometry. The host structure is determined by Rietveld refinement based on powder X-ray diffraction (P-XRD) data. The site-dependent luminescence of Ce³⁺ and Eu²⁺ is discussed on the basis of the Ca₈Mg₃Al₂Si₇O₂₈ structure and low-temperature VUV-UV spectra. Doublet emission bands of Ce³⁺ are located at ∼376 and ∼399 nm, and the emission band of Eu²⁺ is located at ∼536 nm. Due to energy transfer and different thermal behaviors of Ce³⁺ and Eu²⁺ luminescence, the emission color of Ca₈Mg₃Al₂Si₇O₂₈:Ce³⁺,Eu²⁺ is tunable with different doping levels and temperatures under excitation at 320 nm. The energy transfer mechanism between Ce³⁺ and Eu²⁺ is analyzed by the Inokuti–Hirayama model. The ratiometric fluorescence intensity of Eu²⁺ to Ce³⁺ is applied to denote the variation of temperature, and provides sensitivity to the temperature readout. Series of temperature-dependent measurements indicate that the Ca_7.97Ce_0.01Na_0.01Eu_0.01Mg₃Al₂Si₇O₂₈ phosphor is a promising candidate for optical thermometric applications.