Luminescence, energy transfer, and up-conversion mechanisms of Yb3+ and Tb3+ co-doped LaNbO4

Abstract

Novel green-emitting Yb 3+ and Tb 3+ co-doped LaNbO 4 particles were prepared through a facile sol-gel and combustion method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric and differential thermal analysis (TG-DTA), up-conversion luminescence (UCL) with different powers and varied concentrations, and luminescent lifetimes were employed to test the prepared samples. The XRD data exhibit that a sample with high crystallinity can be acquired at 1000 °C. FE-SEM images show homogeneous and spherical grains after Yb 3+ and Tb 3+ are co-doped in the LaNbO 4 samples. TG-DTA reveals that the LaNbO 4 synthetic process is accompanied by a temperature increase. In our work, we utilize a 980 nm laser to excite Yb 3+ ions to achieve the 2 F 7/2 → 2 F 5/2 transition, and the LaNbO 4 :Yb 3+ , Tb 3+ sample exhibits intense green emission. Luminescent spectra at different powers demonstrated the two-photon absorption process; meanwhile, the corresponding energy transfer mechanism from Yb 3+ to Tb 3+ and the emission of Tb 3+ under 980 nm laser excitation was described via an energy level diagram. Moreover, concentration-dependent up-conversion luminescent properties were systematically explored, and it was confirmed that LaNbO 4 :0.15Yb 3+ ,0.02Tb 3+ exhibits the strongest luminescent properties. In particular, as the content of Yb 3+ ions increases, the 5 D 4 → 7 F 6 transition quickly becomes stronger, resulting in the emitted color shifting from green to blue. Therefore, the emitted color can be tuned by adjusting the content of Yb 3+ ions. The excellent up-conversion emission properties of the obtained samples allow for their potential application in the fields of 3D display technologies and 3 solid-state lasers.

Terbium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties

“…The proposed hypothesis, in which Tb presence increases the concentrations of oxygen interstitials and electron holes, could explain this observation. The hole conductivity occurs as a result of the partial reduction of Tb 4+ in the lattice (reaction ( 9)), and this should not be affected by the hydration reactions (11) and (12). Therefore, with increasing terbium content, the hole conductivity also increases and the relative contribution of protons into the total conductivity should decrease.…”

“…For the last decade, multiple rare earth orthoniobates systems have been investigated, with the interest being put on their electronic [9][10][11] along with ionic conduction with oxygen ions [9,10] and protons [3] as mobile charge carriers. Also, other interesting properties were observed in these materials, e.g., paramagnetism, ferroelectricity, and luminescent emission [1,12].…”

Up-conversion properties of Yb,Tb:YAG single crystals grown by the micro-pulling-down method

“…The emission intensity increases gradually with the increase of Yb 3+ concentration from 2 at.% to 8 at.%, because the distance between Yb 3+ and Tb 3+ ions is shortened by the increasing concentration of Yb 3+ , which inducing the improved energy transfer efficiency between rare earth ions and enhanced emission intensity. Then the emission intensity decreases with the further increase of the concentration of Yb 3+ , which is due to quenching effect resulting from the pairing or aggregation of Yb 3+ ions [22]. Fig.…”

“…For the Yb 3+ /Tb 3+ dopants, the mechanism of up-conversion is called cooperative energy transfer (CET), two excited Yb 3+ (sensitizer) ions simultaneously transfer their energy to one Tb 3+ (activator) ion, and the Tb 3+ is excited to the 5 D4 level. In previous literatures, some works had been done in Yb 3+ /Tb 3+ co-doped materials [19][20][21][22]. However, Yb 3+ /Tb 3+ co-doped YAG crystal has never been reported.…”

Praseodymium Orthoniobate and Praseodymium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties

“…The first work focused on ABO 4 type compounds was published by Keller in 1962 [ 1 ], and in the following years, different properties of rare earth orthoniobates have been investigated. Such properties as proton conductivity [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ], dielectric properties in the microwave frequency range [ 9 , 10 ], shape memory effect [ 11 ] and luminescence properties [ 12 , 13 , 14 ] make these materials a very promising group of materials with a wide range of applications.…”