Luminescence and energy transfer processes in GdErAlCrO.

GdErAlO and GdErAlCrO samples were synthesized using a solid-state reaction method. Structural analysis revealed that the samples crystallized in an orthorhombic structure phase with a space group. The average crystallite sizes were around 283 nm and 574 nm for GdErAlO and GdErAlCrO, respectively. Derivative absorption spectrum fitting (DASF) and first-derivative reflectance (d /d) methods confirmed that the samples possess a direct wide band gap, with energies of 5.93 eV and 5.90 eV, respectively. The photoluminescence (PL) spectrum of GdErAlO under = 377 nm excitation exhibits a green emission and intense sharp red lines at 680 nm, 697 nm, 705 nm, 717 nm and 758 nm. The green emission corresponds to the transitions H → I and S → I of Er ions, while the sharp red lines are attributed to transitions between intrinsic defect centers related to the GdAlO host coupled to B (4) and B (7) vibrational modes. Efficient energy transfer resonant phonon-assisted and cross-relaxation processes from Er and intrinsic defect centers to Cr is responsible for the decrease in green and red emission line intensities in GdErAlCrO. The energy transfer from Er and intrinsic defect centers indicates that red emission lines at 697 nm and 726 nm in GdErAlCrO mainly originate from the T (G) → A (F) and E (G) → A (F) transitions of Cr ions.