Structural, thermal, and optical spectroscopic studies of Sm3+-doped Ba2ZnSi2O7 phosphors for optical thermometry applications

Abstract

Samarium-doped Ba₂ZnSi₂O₇ orange red-emitting phosphors for novel applications in temperature measurement were prepared by a solid-state synthesis method. A Ba₂ZnSi₂O₇ akermanite-structured Sm³⁺ phosphor was allocated to the C2/c space group and monoclinic system. Using FTIR, identification of different bonds with their vibrational modes has been done. Stimulated at 403 nm, the as-prepared phosphors show yellow (560 nm), orange (600 and 645 nm), and red (705 nm) emissions, which were also used to maximize the dopant concentration. Sm³⁺ ions may be uniformly dispersed throughout the Ba₂ZnSi₂O₇ matrix, and Sm³⁺ consists of irregular microparticles. Optical energy bandgap values for Ba₂ZnSi₂O₇ and 0.4 mol%Sm³⁺ (∼3.33 eV and ∼3.40 eV) reveal the formation of faulty energy levels in the band gap. Sm³⁺ quenching at an appropriate concentration of 0.4 mol%, with a critical distance of approximately 44.33 Å, and a θ value of 3.93, almost equal to 4, was found to be indicative of the dipole–dipole type of electric multipolar interaction. Excellent thermal stability of the PL peaks was observed in Ba₂ZnSi₂O₇:0.4%Sm³⁺. A novel dual-model thermometry approach based on an adjusted Boltzmann population distribution and an exponential function would be put forward. The Ba₂ZnSi₂O₇:Sm³⁺ phosphor exhibited relative sensitivities of 2.02% K⁻¹ based on modified Boltzmann population distribution through the FIR strategy and temperature-dependent lifetime was also employed to calculate relative sensitivities of 3.25% K⁻¹ based on exponential function. In light of these experimental results, the produced Sm³⁺ doped Ba₂ZnSi₂O₇ phosphors can thus be a promising choice for UV-excitable warm lighting systems and non-contact optical thermometry measurements.