Red-emission analysis, Judd–Ofelt intensity parameters and laser properties of CdMgZnO:xEu³⁺ nanocrystals: the effects of Eu³⁺ concentration

Abstract

In this paper, we discuss a strong red Eu3+-concentration-dependent emission line associated with an electric dipole transition (5D0 → 7F2) at 616 nm in CdMgZnO:xEu3+ nanocrystals made via a sol–gel synthesis route. Oxygen interstitial defects created by the presence of a mixed-valence state of Eu 3+ and Eu2+ ions as rare-earth cations lead to a structural distortion which is confirmed by x-ray photon electron spectroscopy. The Judd–Ofelt intensity parameters, Ω2 and Ω4, obtained from the emission spectra, show a trend for Ω2 > Ω4 that translates to stronger covalence and a stable local structure surrounding the Eu3+ ions in CdMgZnO nanocrystals. The asymmetry ratio (R o), radiative lifetime (), branching ratio , stimulated emission cross-section, and the gain bandwidth (δ e× Δλ eff) for 5D0 are computed and analysed. A radiative lifetime ranging from 789 to 984 µs points to a suitable material for orange-red fluorescent phosphors for lighting and display technologies. The gain bandwidth (δ e× Δλ eff), which is dependent on the Eu3+ concentration, suggests the use of the CdMgZnO:xEu3+ nanocrystal material in fibre amplifiers, while the sample with x = 1.5%, which yields the largest emission cross-section (15.79 × 10−22 cm2), the highest gain bandwidth (28.8 × 10−28 cm3), and a high branching ratio (71%), is the best candidate for red laser applications.