(Ba,Sr)TiO(3):RE perovskite phosphors (RE = Dy, Eu): nitrate pyrolysis synthesis, enhanced photoluminescence, and reversible emission against heating

A series of (Ba,Sr)TiO(3) phosphors singly doped with Eu(3+) and Dy(3+) were successfully synthesized using the nitrate pyrolysis method at 750 °C. Eu(3+) or Dy(3+) single-doped BaTiO(3) retained the tetragonal crystal structure of the host, while the Sr(2+)-substituted (Ba,Sr)TiO(3):RE(3+) (RE(3+) = Eu(3+) or Dy(3+)) experienced a phase transformation from tetragonal to cubic phase with a unit cell shrinkage. For Eu(3+) doped phosphors, BaTiO(3):xEu(3+) (x = 0.02–0.10) exhibited red photoluminescence and the highest intensity of emission belonged to the optimal-doped BaTiO(3):xEu(3+) (x = 8 mol%). Moreover, the substitution of 30 mol% Sr(2+) for Ba(2+) (that is Ba(0.7)Sr(0.3)TiO(3):xEu(3+), x = 8 mol%) further enhanced the emission intensity of BaTiO(3):xEu(3+) (x = 8 mol%). For Dy(3+) doped phosphors, BaTiO(3):xDy(3+) (x = 0.02–0.10) showed yellow photoluminescence and the highest light intensity was from the optimal-doped BaTiO(3):xDy(3+) (x = 4 mol%). In addition, the substitution of 20 mol% Sr(2+) for Ba(2+) (the phosphor Ba(0.8)Sr(0.2)TiO(3):xDy(3+), x = 4 mol%) induced further increase in emission intensity of BaTiO(3):xDy(3+) (x = 4 mol%). The emission intensities at higher temperature of 100 °C retained about 70% and 90% of the initial values at room temperature (RT) for the optimal BaTiO(3):xEu(3+) (x = 8 mol%) and BaTiO(3):xDy(3+) (x = 4 mol%) phosphors, respectively, while the emission intensities at the temperature of 100 °C retained about 60% and 80% of the initial intensities at RT for the optimal Sr(2+)-substituted Ba(0.7)Sr(0.3)TiO(3):xEu(3+) (x = 8 mol%) and Ba(0.8)Sr(0.2)TiO(3):xDy(3+) (x = 4 mol%) phosphors, respectively. It is worth noting that on cooling down to RT again from 210 °C, the BaTiO(3):xDy(3+) (x = 4 mol%) phosphor exhibited excellent luminescent thermal stability (with a high activation energy of 0.387 eV) and the strongest recovery (∼95%) of PL emission among the series of phosphors. The as-prepared phosphors with optimal compositions would be good candidates for the applications in lighting, display, and related fields.