Energy transfer dynamics and luminescence properties of Eu³⁺ in CaMoO₄ and SrMoO₄

Abstract

Undoped and europium doped CaMoO4 and SrMoO4 scheelites are synthesized using a complex polymerization method. The phase purity of the sample is confirmed using powder X-ray diffraction (PXRD). X-ray photoelectron spectroscopy (XPS) was carried out to confirm the oxidation states of various constituents and dopant elements and also the presence of oxygen vacancies. Interestingly both CaMoO4 and SrMoO4 on irradiation with UV light give blue and green emission respectively. On europium doping, it was found that molybdate to Eu(3+) ion energy transfer is more efficient in SrMoO4:Eu compared to CaMoO4:Eu. It is also justified using a luminescence lifetime study which shows biexponential decay in the case of CaMoO4:Eu corresponding to both the host and europium ion; whereas a single lifetime is observed in the case of SrMoO4:Eu. Anomalies in host-dopant energy transfer are suitably explained using density functional theory (DFT) calculations and XPS. The actual site symmetry for the europium ion in CaMoO4 and SrMoO4 was also evaluated based on a Stark splitting pattern which turns out to be D2 and C2v respectively although it is S4 for Ca/Ba(2+) in AMoO4. This is also reflected in higher Ω2 values for SrMoO4:Eu than CaMoO4:Eu.

Red and green colors emitting spherical-shaped calcium molybdate nanophosphors for enhanced latent fingerprint detection

“…The opposite was observed due to the polarization effect of MoO 4 2− moieties present in the host lattice and it also affects the luminescence of the sample. The MoO 4 2− moieties of the host lattice are useful to get strong emission from activator ions by transferring the absorbed excitation energy non-radiatively to the Eu 3+ ions 12 . The emission colors from the powder sample and the powder dispersed in DI water were snapped under normal and UV lights and are shown in the inset of Fig.…”

“…However, different types of host materials were studied and oxide-based materials were of significant interest because of their lower toxicity and robustness 11 . Metal molybdates of general formula AMoO 4 (A = Ca, Sr, Ba) are one of the oxide-based host materials which give excellent luminescent properties due to the property of energy transfer from host lattice to the dopant ions 12, 13 . Among these metal molybdates, CaMoO 4 is one of the host materials which belong to the scheelite family having tetragonal structure with a space group of I41/a.…”

Multicolor Tuning in Room‐Temperature Self‐Activated Ca2Nb2O7 Submicroplates by Lanthanide Doping

“…It has shown a wonderful prospect in multicolor lighting and displays by combining the designed phosphors with a matched LED chip as an excitation source. Obviously, the broadband emission from self‐activated phosphors plus the characteristic luminescence from the doped Ln 3+ ions is more suitable to acquire a desirable colored light including white light, indicating a bright prospect for multicolor tuning ,…”

Revealing the substitution mechanism in Eu3+:CaMoO4and Eu3+,Na+:CaMoO4phosphors

“…The excellent luminescent properties together with the high chemical and thermal stability of the CaMoO4:Eu 3+ phosphor has attracted a lot of attention in the last decade. Photoluminescence properties of CaMoO4:Eu 3+ have been extensively studied in bulk samples, 5,6,7,8 microparticles 3,9,10,11 and different types of nanoparticles. 12,13,14,15 However, very little attention has been paid to the substitution mechanism and crystal structure of Eu 3+ :CaMoO4 phosphors.…”