Effects of Defect Density on Optical Properties Using Correlative Cathodoluminescence and Transmission Electron Microscopy Measurements on Identical PrNbO₄Particles

Abstract

Understanding the optical properties of lanthanide niobates is essential to improve the development of these materials. In this study, we investigated PrNbO 4 powder particles with different density of twins which influences the intensity of the emission lines. The twins form during synthesis of these particles based on a solid-state route. A correlative approach using backscattered electron imaging, cathodoluminescence measurements, focused ion beam lift out, and aberration-corrected transmission electron microscopy was used at the same location within the particles. Emission lines were acquired by using a cathodoluminescence spectrometer attached to a scanning electron microscope on two regions including twinned and twin free areas. The results were compared and indicate that the areas with higher density of twins have more intense emission lines. The reason for the improved luminescent properties is the perturbation of the energy states caused by the defects which promotes the occurrence of the parity forbidden f−f transitions.

Combined structural analysis and cathodoluminescence investigations of single Pr3+-doped Ca2Nb3O10 nanosheets

“…On the basis of these results and our previous publications 10 , 11 , we conclude that bulk particles (PrNbO 4 and Pr 3+ : Ca 2 Nb 2 O 7 ) have brighter emission lines (especially transitions belonging to the dominant peaks: 3 P 0 - 3 H 4 and 3 P 2 - 3 F 4 ) due to their much higher Pr content. However, 2D nanosheets (Pr 3+ : CaNb 3 O 10 ) with additional sharp emission lines around 600 nm and smaller size are potential candidates to be used in other applications where the mentioned wavelength (orange color) is needed.…”

“…The simulations were done to determine the thickness of the sheets and indicate the atomic positions of Nb, Ca and O. According to 10 , 11 , possible sites substituted by Pr could be Ca and Nb. The corresponding thickness-defocus map is shown in Fig.…”

“…The optical properties of individual nanosheets with different thicknesses are correlated to their crystal structure and chemical composition obtained via transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). We found that due to the lower Pr content observed in the nanosheets compared to bulk particles 10 , 11 , different luminescence properties are observed.…”

Ultrafast synthesis and luminescence properties of rare earth orthoniobates RENbO4 (RE = La, Eu, Gd, Yb, Lu)

“…In figure 5, the broad absorption band of 200-400 nm is the charge transfer transition band, which corresponds to the transition of the O 2− 2p orbital to the Nb 5+ 4d orbital. The 395 nm, 466 nm, and 537 nm absorption peaks of EuNbO 4 correspond to 7 F 0 → 5 L 6 , 7 F 0 → 5 D 2 and 7 F 1 → 5 D 1 transitions. Yb 3+ ion has a large absorption cross-section at about 980 nm, and the corresponding transition is 2 F 7/2 → 2 F 5/2 .…”

“…The rare earth niobates have different stoichiometric ratios of RENbO 4 , RE 3 NbO 7 , * Authors to whom any correspondence should be addressed. RENb 3 O 9 , RENb 5 O 14 , and RENb 7 O 19 [7][8][9]. Among these phases, RENbO 4 has self-activated properties and strong absorption broadband in the ultraviolet region, which can be used as an energy sensitizer to improve the luminescence intensity of lanthanide ions.…”