On the Pr3+ activated and Li+ co-doped α-Sr2P2O7 for high-energy excitation

Pr 3+ activated α-Sr 2 P 2 O 7 pyrophosphate were obtained as single-phase samples by Li + charge compensation resulting in high optical quality samples. These were thus investigated under vacuum-ultraviolet (VUV), xenon excimer lamp, and X-ray excitation to characterise its suitability as deep ultraviolet-C (UVC) phosphor. The rigid P 2 O 7 4- framework and two distinct Sr 2+ sites enable Pr 3+ incorporation without structural distortion, consistent with Vegard’s law and the ionic-radius tolerance of the host lattice. Under VUV excitation the onset of host assisted population of the Pr 3+ 5d levels is observed and the emission consists of a structured set of deep UVC bands originating from [Xe]4f 1 5d 1 → [Xe]4f 2 whose relative intensities change systematically with Pr 3+ concentration. This behaviour is attributed to a concentration dependent redistribution of Pr 3+ between the two Sr 2+ sites which differ in anion polarizability and crystal field strength. X-ray excitation confirms the same qualitative spectral trends but reveals an earlier onset of concentration quenching which is attributed to bulk dominated non-radiative processes including defect complexes possible Pr 3+ clustering and self-absorption effects. Together these results establish a clear structure property relationship and demonstrate that α-Sr 2 P 2 O 7 Pr 3+ is a rather efficient UVC phosphor whose optimal Pr 3+ concentration depends on the excitation regime, indicating their suitability for phosphor applications operated under high-energy excitation, such as excimer/exciplex sources or cathode/X-ray–driven converter systems. • Single-phase α-Sr 2 P 2 O 7 :Pr 3+ ,Li + synthesized with high optical quality • Deep UVC emission from Pr 3+ [Xe]4f 1 5d 1 → [Xe]4f 2 under high energy excitation • Pr 3+ redistribution between two Sr 2+ sites controls UVC band intensities • X-ray excited luminescence shows earlier concentration quenching • Optimal Pr 3+ concentration depends on the excitation regime