Photoluminescence upgradation of La2MgTiO6:2%Dy3+ perovskite with monovalent (Li+), divalent (Ba2+, Sr2+) and trivalent (Bi3+, Sm3+) cation sensitization

Abstract

Nano phosphors of 2% Dy³⁺ (wt%) doped La₂MgTiO₆ and monovalent/divalent/trivalent co-doped La_1.98Dy_0.02MgTiO₆:x%A^y+ (A^y+: Li⁺, Ba²⁺, Sr²⁺, Bi³⁺, and Sm³⁺; 0 ≤ x ≤ 2 wt%) were synthesized by combustion method. From the XRD data, it is deduced that an increase in the valency of co-dopant increases the crystallinity of the double perovskite orthorhombic nanocrystal structure. With an increase in co-dopant size, an elevation in optical bandgap is visible with the highest bandgap of 3.835 eV for Bi³⁺. The photo-absorption is monotonically broadened for Sr²⁺, Sm³⁺, and Li⁺ around 200–450 nm. Under 351 nm, Dy³⁺ triggered lattice shows major characteristic emission peaks at 480 nm (⁴F_9/2 → ⁶H_15/2), 574 nm (⁴F_9/2 → ⁶H_13/2), and 670 nm (⁴F_9/2 → ⁶H_11/2), leading to near white light emission with CIE coordinates (0.341, 0.376). Upon co-doping, the PL intensity is significantly increased with maximum emission for trivalent Sm³⁺, followed by divalent Sr²⁺ and monovalent Li ⁺ respectively. With increasing excitation wavelength, Sr²⁺ shows a dominated output and it is found that divalent Sr²⁺ is a potential co-dopant that could enhance luminescence intensity up to 6 times with a Sr²⁺ → Dy³⁺ energy transfer efficiency of 86%. It is specified that the CIE coordinates of Li⁺ co-doped samples show ideal white emission with color coordinates (0.333, 0.336). The concluding outcomes signify the noblest rare earth Sm³⁺ co-doping and thus Sm³⁺ → Dy³⁺ energy transfer mechanism is discussed in detail.