Enhancement of Photoluminescence in CaTiO₃:Pr³⁺ by Ba and Sr Substitution for Ca

Abstract

Photoluminescence properties were improved in CaTiO3:Pr3+ phosphor by substitution of Ba and Sr for Ca to a large extent of Ba (0–20%) and Sr (0–45%) fractions. Red emission intensity at 612 nm was greatly enhanced. It achieved its largest value in Ca0.7Sr0.3TiO3:Pr3+ sample, higher by 192% than CaTiO3:Pr3+. Enhancement of red emission in Ba and Sr added CaTiO3:Pr3+ is inferred to originate from improvement of Pr3+ 4f5d capture probability to electrons in the host conduction band and charge transfer state, which are lowered by Ba and Sr addition.

Blue excited photoluminescence of Pr doped CaBi2Ta2O9 based ferroelectrics

“…The reasons for the enhancement of the PL intensity can be ascribe to the change of the lattice symmetry. The change of the lattice symmetry will give rise to a remarkable effect on the properties of Pr 3+ and further influence the luminescence properties [31][32][33][34], when Ca 2+ (1.34Å, 12 CN) ions are replaced by bigger radius Sr 2+ ions (1.44Å, 12 CN), the symmetry of the pseudoperovskite units was changed [33]. As previously discussed Pr 3+ ions dispersed in the pseudo-perovskite units of samples' crystal structure.…”

Enhancement of luminescence and afterglow in CaTiO3:Pr3+ by Zr substitution for Ti

“…It is worth to note that there is no change of the absorp- tion edge by Zr 4+ substitution for Ti 4+ . This observation is different from the red shift of the absorption edge due to divalent metal ions, such as Ba 2+ and Sr 2+ , substitution for Ca 2+ in CaTiO 3 :Pr 3+ [13]. B band is attributed to a low-lying Pr-to-metal intervalence charge transfer state (IVCT), by which photo-electrons are radiationlessly de-excited from the 3 P 0 state to the 1 D 2 state of the Pr 3+ ions [6,19].…”

“…However, the 4f5d band of Pr 3+ is very sensitive to the host crystalline environment. The presence of a crystal field in most crystalline hosts would shift the 5d energy level of Pr 3+ and allows more strong 4f-4f emission to occur [13,23]. The increased emission is shown in Fig.…”

“…Among them, CaTiO 3 :Pr 3+ is of special interest due to its red emission with appropriate CIE coordinate (0.680, 0.311), which is very close to that of the 'ideal red' [1]. To improve the luminescence intensity and enhance the afterglow efficiency of this perovskite material, many efforts have been done [2,3,[10][11][12][13][14][15]. It is known that there exist two ways for increasing the emission intensity.…”

“…Using monovalent cations including Na + , Tl + , or Ag + substitution for Ca 2+ [2], trivalent cations such as Al 3+ [10] or Ln 3+ (Ln = La, Lu, Gd) [11] substitution for Ti 4+ , or using calcium vacancy compensation method [12] have been reported. Another way is to substitute Ca 2+ with equivalent cations, such as Zn 2+ , Mg 2+ [3], Ba 2+ , or Sr 2+ [13]. On the other hand, the afterglow time of the red-emitting CaTiO 3 :Pr 3+ phosphors can be enhanced by substituting Zn 2+ for Ca 2+ site [14,15], or Al 3+ [16], Lu 3+ [11] for Ti 4+ site.…”