Calcination-Free Persistent Luminescence in Hydrothermally Synthesized Pr3+-Doped Ba,CaTiO3 Nanoparticles

Persistent luminescent materials typically require high-temperature calcination to generate trapping centers, limiting their synthesis under mild conditions. Herein, Pr³⁺-doped barium calcium titanate nanoparticles with different Ca/Ba ratios were successfully synthesized by a solvothermal route, exhibiting efficient persistent luminescence without post-synthesis thermal treatment. Structural analyses revealed a gradual transition from tetragonal BaTiO₃ to orthorhombic CaTiO₃ with increasing Ca content. XPS and optical spectroscopy indicated that partial Ba incorporation modulates the defect chemistry through the Pr³⁺/Ti⁴⁺ ⇌ Pr⁴⁺/Ti³⁺ charge compensation mechanism, promoting the formation of charge trapping centers. The sample containing 95 mol% Ca exhibited the highest emission intensity, quantum yield, and persistent luminescence, outperforming both fully substituted compositions and samples prepared by the conventional solid-state route. These findings demonstrate that the control of composition and defect chemistry through solvothermal synthesis provides an effective strategy for developing high-performance persistent phosphors without post-synthesis calcination, with potential applications in photonics, sensing, and bioimaging.