The PL decay curves (Figure 2c) show a significant increase in lifetime from 2.61 ms (PG) to 6.52 ms (glass composite). While the authors attribute this to Tb³⁺ incorporating into the crystal lattice, a change in the local environment can also affect the non-radiative rates. The primary evidence for successful substitution should be a change in the crystal lattice parameter (as mentioned). Did the authors calculate the Tb³⁺ distribution coefficient between the glass and crystal phase? If the crystal phase is a pure host (Na₃YSi₃O₉) and the glass is rich in Tb, the calculated average Tb concentration in the composite might be misleading. This misinterpretation of the distribution could significantly affect the analysis of scintillation yields.
