Up-conversion luminescence and multimodal temperature sensing behaviors in the visible and infrared region of Er3+ and (Er3+, Yb3+) ions in Ca3Ta2Ga3O12 phosphors

Ca3Ta2Ga3O12 - CTGG ceramic phosphors doped with xEr(3+) ions, x = (0.1, 1, 3, 5, 7, and 9 at.%) and (5Er, yYb), y = (0.1, 1, 3, 5, and 7 at.%) were investigated. The emission spectra of Er3+ ions were measured under 973 nm and 1550 nm excitations and the optimal concentrations of Er3+ and (Er3+, Yb3+) ions allowing to obtain the maximum emission intensities in the visible range were determined to be 5Er and (5Er, 5Yb), respectively. The best results in terms of correlated color temperature (CCT) and color purity (CRI) were obtained under lambda(ex) = 973 nm. High values of CCT (between 5000 K and 6000 K) and CRI (in the range of 80-92) parameters indicate their potential as efficient materials for white light-emitting diode devices. The temperature dependence of Er3+ luminescence in 5Er:CTGG and (5Er, 5Yb):CTGG samples was investigated by the luminescence intensity ratio for different thermally coupled (TCLs) and non-thermally coupled (NTCLs) levels and the fluorescence lifetime. The highest value of the relative thermal sensitivity parameter (Sr) for 5Er:CTGG sample, Sr = 1.41 % K-1 at 325 K, was obtained from TCLs (H-2(11/2)/S-4(3/2)) under lambda(ex) = 973 nm. For (5Er, 5Yb):CTGG sample, the highest values of Sr were obtained as follows: Sr = 1.77 % K-1 at 325 K from TCLs (H-2(11/2)/S-4(3/2)), Sr = 1.19 % K-1 at 150 K from TCLs (I-4(13/2)(2)/I-4(13/2)(3)), and Sr = 0.62 % K-1 at 450 K from S-4(3/2) lifetime, under lambda(ex) = 973 nm, and Sr = 1.23 % K-1 at 325 K from TCLs (H-2(11/2)/S-4(3/2)) and Sr = 1.21 % K-1 at 325 K from NTCLs ((H11/2F9/2)-H-2-F-/4) under lambda(ex) = 1550 nm. These results indicate that 5Er:CTGG and (5Er, 5Yb):CTGG ceramic phosphors have high potential for applications in the field of optical temperature sensors.