Optical characterization of rare-earth activated La2-xLnx (MoO4)3 (Ln=Dy, Sm) phosphors

• Published in: Journal of molecular structure Vol. 1281; p. 135111
• Main Authors: R, Satheesh, Venugopal, Meenu, P, Anusree S., S, Dhanya V., Padma Kumar, H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.06.2023
• Subjects: Band gap; CCT; CIE and color purity; Co-doping; Lifetime; Orange-red emission; Photoluminescence; Solid-state synthesis; Lifetime; CCT; Photoluminescence; Co-doping; Solid-state synthesis; Orange-red emission; Band gap; CIE and color purity
• DOI: 10.1016/j.molstruc.2023.135111
• ISSN: 0022-2860

·La2-xDyx(MoO4)3 and La2-xSmx(MoO4)3 phosphors were synthesized using traditional solid-state ceramic route.·Intense yellow emission of Dy3+ and reddish-orange emission of Sm3+ revealed that the activators occupied a low symmetry site in the host.·Excitation wavelength tunable near-white emissions of Dy3+ activated La2(MoO4)3 with small emission life time and low colour purity marked them an ideal candidate for WLED applications.·High colour purity and sub millisec emission lifetime of Sm3+ activated La2(MoO4)3 showed the suitability of these phosphors for high speed switching application.·Effect of co-doping with Sm3+ and Dy3+ on Lanthanum molybdate were also investigated.·Co-doping results in the shifting of CCT from cold to warm emissions. Dysprosium and Samarium doped Lanthanum molybdate (La2-xLnx(MoO4)3, Ln=Dy/Sm) powders were synthesized by the conventional solid-state ceramic route. X-ray diffraction studies confirmed the monoclinic phase of the samples with space group c2/c. Diffuse reflectance and photoluminescence spectrum revealed the optical properties of La2-xLnx(MoO4)3 samples. The band gap of doped La2-x(MoO4)3:x(Dy/Sm) shows a linear dependence on the doping concentration of rare-earth up to an optimum concentration. Low-symmetry site of Dy3+within the La2(MoO4)3 host resulted in a sharp yellow emission peak (575 nm) that dominates over blue emission (481 nm). Sm3+ doped samples showed intense orange-red emissions under an excitation wavelength of 404 nm. The variation of the lifetime of the luminescence peaks was studied in detail and the CIE colour coordinates and correlated colour temperature were calculated for varying rare-earth concentration as well as excitation wavelength to ascertain their suitability in phosphor applications. Dy3+ doped La2(MoO4)3 powders showed near white light emission and Sm3+ doped La2(MoO4)3 powders showed sharp emission in the orange-red region. Sharp excitation bands in near-UV (NUV) region in the luminescence spectra of La2-xDyx(MoO4)3 and La2-xSmx(MoO4)3 compounds establish the prospects of using these samples in NUV -LED applications. To investigate the effect of Sm3+ and Dy3+ co-doping on Lanthanum molybdate, a series of compounds of composition La1.8-xDy0.2Smx(MoO4)3 (x = 0.005, 0.02, 0.04 and 0.06) and La1.925-xSm0.075Dyx(MoO4)3 (x = 0.005, 0.02 and 0.04) were synthesized by the solid-state ceramic route. The effect of co-doping on the luminescence, CIE colour coordinates, correlated colour temperature and colour purity were studied.