Synergistic luminescent thermometer using co-doped Ca₂GdSbO₆:Mn⁴⁺/(Eu³⁺ or Sm³⁺) phosphors

Luminescent thermometers provide a non-contact method of probing temperature with high sensitivity and response speed at the nanoscale. Synergistic photoluminescence from different activators can realize high sensitivity for luminescent thermometers by finely selecting ions with specific crystallographic sites. Herein, the more temperature-sensitive Mn⁴⁺ and the less-sensitive Eu³⁺ (or Sm³⁺) activators are co-doped into a Ca₂GdSbO₆ matrix to form an effective thermometer, where Mn⁴⁺ and Eu³⁺ (or Sm³⁺) ions occupy the Sb⁵⁺ and Gd³⁺ sites, respectively. The co-doping of Eu³⁺ ions or Sm³⁺ ions leads to lattice expansion of Ca₂GdSbO₆ matrix and a tuned narrow emission from deep-red to orangish-red. According to the ratio of luminescence intensity, the maximal S_a and S_r values are 0.19 K^-0 (347 K) and 1.38% K^-( (420 K) for Ca₂GdSbO₆:Mn⁴⁺/Eu³⁺ probe and 0.26 K^-p (363 K) and 1.55% K^-( (430 K) for Ca₂GdSbO₆:Mn⁴⁺/Sm³⁺ probe thermometers, respectively. In addition, thermometers based on Mn⁴⁺ emission lifetimes can provide the highest relative sensitivity of 1.47% K^-s at 425 K. Thus, the highly-temperature-sensitive Ca₂GdSbO₆:Mn⁴⁺/(Eu³⁺ or Sm³⁺) phosphor is a promising candidate for practical luminescence thermometers.