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KGd(PO 3 ) 4 (KGP) glasses doped with 3.0 mol% Ce 3+ and systematically varied K 2 O:Gd 2 O 3 ratios were prepared by the melt-quenching method and exhibit pronounced composition-dependent optical and scintillation properties. FTIR analysis revealed progressive network depolymerization with increasing K 2 O content, as evidenced by an increase in the average number of non-bridging oxides from 1.41 to 1.64. In the transmission spectra, the Ce 3+ 4 f –5 d absorption band was observed in all samples, and the band exhibited a pronounced wavelength shift depending on the compositional ratio. When the composition deviated from the stoichiometric KGP (becoming either Gd-rich or K-rich), the absorption and photoluminescence (PL) band red-shifted in both cases: in the Gd-rich samples due to crystal-field strengthening associated with reinforcement of the phosphate network, and in the K-rich samples due to the nephelauxetic effect arising from increased optical basicity, both of which induce a low-energy shift of the Ce 3+ 5 d level. The absolute PL quantum yield ( QY ) peaks at 81.1% for stoichiometric KGP and decreases sharply with off-stoichiometric deviation; at the same time, the PL decay time constant shortens, indicating increased nonradiative loss and a reduced radiative fraction in the off-stoichiometric glasses. The integrated photoacoustic (PA) intensity is minimal at the stoichiometric KGP sample and increases toward both extremes; the scintillation light yield ( LY ) is anti-correlated with PA intensity and positively correlated with PL QY . Under γ-ray excitation, the stoichiometric KGP sample exhibits the maximum LY (∼2,860 photons/MeV) and a low afterglow (∼2.08 × 10 1 ppm), lower than Tl:CsI (1.09 × 10 2 ppm). These results indicate that changes in glass structure due to adjustments in K 2 O:Gd 2 O 3 significantly affect scintillation performance. • Melt-quenched KGd(PO 3 ) 4 glasses doped with 3.0 mol% Ce 3+ were successfully synthesized with systematically varied K 2 O∶Gd 2 O 3 ratios. • FTIR analysis demonstrates network depolymerization, with the average number of non-bridging oxygens increasing from 1.41 to 1.64 as K 2 O content increases. • FTIR-derived network structure combined with optical basicity analysis elucidated that the Ce 3+ 4 f –5 d absorption and emission bands red shift due to crystal field strengthening in Gd-rich compositions and a nephelauxetic effect in K-rich compositions. • The stoichiometric KGd(PO 3 ) 4 composition (K 2 O:Gd 2 O 3 = 1:1) achieves a maximum photoluminescence quantum yield of 81.1% and a scintillation light yield of ∼2,000 photons/MeV. • Afterglow level of ∼2.08 × 10 1 ppm for the stoichiometric glass is lower than that of Tl:CsI counterpart (1.09 × 10 2 ppm).
Shiratori et al. (Tue,) studied this question.