J. Eur. Opt. Society-Rapid Publ. 22, 18( 2026) 167
Figure 2. Emission spectra of YAG: 1 % Pr 3 + samples annealed to different temperatures.
increasing the annealing temperature to 1600 ° C, a nearly single-phase YAG sample is obtained( YAG = 99.1 wt.%, YAP = 0.3 wt.%, YAM = 0.6 wt.%).
3.2 Emission spectra
The measured emission spectra of YAG: 1 % Pr 3 + powders are shown in Figure 2.
As can be seen in Figure 2, the intensity of the emission lines varies with the temperature at which the crystalline phases were formed, showing an overall increase in peak intensities with increasing formation temperature. The intensities of the two strongest peaks exhibit distinct trends with annealing temperature: the 488 nm line increases more markedly, while the 611 nm line shows a comparatively weaker dependence. After thermal annealing at 1100 ° C for 2 h, the luminescence is too weak to reliably determine the intensities of the 488 nm and 611 nm peaks.
Accordingly, the intensity ratio of the 3 P 0? 3 H 4( 488 nm) and 1 D 2? 3 H 4( 611nm) transitionswasmeasured as a function of annealing temperature( Fig. 3).
A linear increase in the 3 P 0? 3 H 4 / 1 D 2? 3 H 4 peak intensity ratio with increasing annealing temperature allowed calibration from 1300 to 1600 ° C. The slope, determined by least-squares fitting, was 0.001 ± 7.49 10 �5 ° C �1, defining the powder’ s temperature sensitivity.
3.3 Fluorescence decay time
An analysis of the change in excited-state decay times under the influence of temperature in the range of 1100 ° C to 1600 ° Cwascarriedout. Figure 4 presents the examination of the 1 D 2? 3 H 4 transition.
Changes in the annealing temperature of the luminescent powder also affect the lifetimes of the excited states. As the annealing temperature increases, the luminescence decay time becomes shorter. At 1600 ° C, a single-phase
Figure 3. Change of peak intensity ratios as a function of temperature in YAG: 1 % Pr 3 + powder.
YAG sample with high symmetry and a regular crystal structure is obtained. Such a homogeneous environment promotes radiative transitions and stronger electron – photon interactions, resulting in shorter decay times.
At lower annealing temperatures, the powder is multiphase, initially composed mainly of YAM and YAP phases. Upon heating, these phases irreversibly transform into YAG, creating a more homogeneous environment as the temperature rises. The evolving crystal structure modifies the crystal field symmetry and the local environment of the active Pr 3 + ions, thereby altering the intensity parameters and probabilities of electronic transitions. Consequently, the lifetime of the 1 D 2 level decreases as the annealing temperature increases.