Thermal‐couple levels of 4S3/2 and 2H11/2 in Na(Ca, Sr)La(VO4)2:Er3+ phosphors for potential optical thermometers

Abstract Novel green‐emitting erbium(III) (Er 3+ )‐activated Na(Ca, Sr)La(VO 4 ) 2 phosphors with an interesting and stable trigonal structure were prepared. The crystal structure, elemental composition, morphology, photoluminescence, and sensing properties were investigated in detail. The color purity values of optimal NaSrLa(VO 4 ) 2 :0.05Er 3+ and NaCaLa(VO 4 ) 2 :0.05Er 3+ phosphors were calculated to be about 92.91% and 90.73% with the Commission Internationale de I’Eclairage color coordinates of (0.283, 0.684) and (0.295, 0.676), respectively. Meanwhile, the sensing property and cycling performance of those samples were also studied based on the thermal‐couple levels of 4 S 3/2 and 2 H 11/2 . The maximum absolute sensing sensitivity values of the NaCaLa(VO 4 ) 2 :Er 3+ and NaSrLa(VO 4 ) 2 :Er 3+ phosphors were found to be 9.23 × 10 −3 and 7.69 × 10 −3 K −1 while the relative sensing sensitivity values were found to be 1.15% and 1.20% K −1 , respectively. Furthermore, several repeated tests confirmed that the cycling performance was stable, demonstrating that the resultant samples with high and stable sensing sensitivity are great potential for optical thermometers.