Comprehension of the photoinduced charge transfer assisted energy transfer in Gd 3+ -based host sensitized tellurate phosphors for thermal sensing and anticounterfeiting labels

A series of novel Eu -activated Ba Gd TeO (BGT) phosphors were successfully synthesised a high temperature solid state reaction method. The crystal structure analysis showed that Eu -doped Ba Gd TeO double perovskite phosphors possess monoclinic symmetry with space group 2 / . The as-prepared phosphors can be efficiently excited by far-ultraviolet light to generate reddish orange luminescence of around 593 nm corresponding to the D → F transitions of Eu ions. Gd acts as a sensitizer for luminescence enhancement. The highest luminescence intensity corresponded to = 0.11 Eu concentration, and the critical distance was calculated to be 9.61 Å, indicating that multipolar interaction is behind the concentration quenching mechanism. Besides, the optimum concentration Eu -activated Ba Gd TeO phosphor exhibited color co-ordinates of (0.63, 0.36), a high color purity of 94.21% and a quantum efficiency of 18%. JO intensity parameters reveal the slight distortion of the crystal field around the activator ion. Notably, the maximum relative sensitivities of the BGT:0.11Eu phosphor were found to be 0.19% K within the temperature range of 300-500 K and 2.07% K within 80-300 K, and it can potentially be used as a promising thermometer in high and low temperature regions, respectively. The luminescent labels based on fluorescent ink and PL chalk demonstrate the potential application of synthesized phosphors in anti-counterfeiting and security labeling.