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 La1.98Dy0.02MgTiO6:x%Ay+ (Ay+: 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 (4F9/2 → 6H15/2), 574 nm (4F9/2 → 6H13/2), and 670 nm (4F9/2 → 6H11/2), 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.