A New Look at the Explanation of Differences in Properties between La³⁺ and Lu³⁺ Titanate Hosts Occupied by Eu³⁺

Abstract

In order to improve the quality of WLEDs, considerable efforts have been devoted to investigate red phosphor. In this study, two double perovskites La 2 MgTiO 6 and La 2 ZnTiO 6 and two novel pyrochlores Lu 2 MgTiO 6 and Lu 2 ZnTiO 6 doped with 1%Eu 3+ were synthesized by the co-precipitation method. The crystal structure, absorption, excitation, and emission spectra of all samples were investigated in detail. Dissimilar luminescent behaviors of the studied samples were observed. Due to the different site symmetry of Eu 3+ , each compound exhibits a different emission spectrum. The emission of the magnetic dipole transition is dominant in all the spectra of the Lu-based hosts, while the forced electric dipole transition is the strongest one in the spectra of the others. Besides, the ones crystallized in double perovskite structures possess larger bandgaps and show a more intense emission from the 5 D 1 level of Eu 3+ as compared to the pyrochlore compounds. Furthermore, the distinct mechanism of the crossrelaxation of four titanate compounds was investigated. The above findings contribute to the understanding of the two novel pyrochlore hosts.

Physicochemical Characterization of the Hybrid Molybdate–Tungstate Materials for Solid-State Lighting

“…Photoluminescent materials based on rare earth elements have been attractive for novel fluorescent probes, effective spectral converters for solar cells, , used in an anticounterfeiting application, optical sensors for oxygen detection, and used in solid-state lighting, ,− general fluorescent lamps, energy-saving lamps, and white light-emitting diodes (W-LEDs). − W-LEDs are the next-generation light source because of their high luminous efficiency, long lifetime, high thermal stability, , absence of pollution, ,, and low price. , For this reason, W-LEDs are a prospective replacement for conventional light sources. , Nowadays, commercial white LEDs available in the market are produced by combining a blue LED chip with yellow (YAG:Ce 3+ ) phosphors. Regrettably, this combination lacks a red component, rendering it poor quality for indoor lighting due to its high correlated color temperature (CCT > 6000 K) and low color rendering index (CRI, Ra < 80).…”