Nanometer-thin layered hydroxide platelets of (Y0.95Eu0.05)2(OH)5NO3·xH2O: exfoliation-free synthesis, self-assembly, and the derivation of dense oriented oxide films of high transparency and greatly enhanced luminescence

Well-defined crystallites autoclaved from the nitrate/NH4OH reaction system as the precursor for (Y,Eu)2O3 red phosphor: Crystallization mechanism, phase and morphology control, and luminescent property

“…The hexagonal platelets can be indexed to a layered rare-earth hydroxide (LRH) phase of Ln 2 (OH) 5 NO 3 Á 1.56H 2 O ( Fig. 2(a), Ln¼Y and Eu) [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], where the hydration number was determined via TG analysis up to 260 1C (Fig. S11).…”

“…The most familiar rare-earth precursor compounds are hexagonal Ln(OH) 3 [18][19][20] and monoclinic Ln 4 O(OH) 9 NO 3 [19,20,24] (Ln¼rare earth ions). Recently, some new rare-earth compounds including anion-exchangeable layered hydroxides Ln 2 (OH) 5 (A mÀ ) 1/m Á nH 2 O (Ln¼La, Pr, Nd, Sm-Tm, and Y, A¼intercalated anions) [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], layered hydroxides Yb 2 (OH) 5 NO 3 Á 2H 2 O and Yb 2 (OH) 5 NO 3 Á H 2 O with coordinated NO 3 À accommodated in the gallery of hydroxide layers [43], anion-exchangeable oxy-hydroxide Yb 3 O(OH) 6 Cl Á 2H 2 O with one-dimensional channels containing uncoordinated Cl À [44], and layered hydroxides Ln 2 (OH) 4 SO 4 Á 2H 2 O pillared by sulfate ions [45,46] are reported, and the crystal structures are systematically investigated. The nitrate/NH 4 OH reaction system is one of the simplest for Y 2 O 3 :Eu 3 þ synthesis.…”

Recent progress in layered rare-earth hydroxide (LRH) and its application in luminescence

“…On the other hand, the nanosheets exfoliated from 251-LRHs tend to orient themselves with a certain crystallographic direction perpendicular to the substrate surface, owing to their significantly two-dimensional morphologies, which may introduce additional or greatly enhanced functionalities. The projection in the [001] direction for the 251-LRH crystal and in the [111] direction for the derived cubic oxide (Ln 2 O 3 ) present close similarities in terms of the atomic configuration of Ln, and thus the phase transformation from LRH to Ln 2 O 3 occurs quasi-topotactically [19]. In view of these, a number of studies have been focused on the construction of oriented fluorescent films, and the transparent oxide phosphor films of the Y/Eu [19,25], Y/Tb/Eu [27], Y/Gd/Eu [21], and Y/Gd/Dy [29] systems with a uniform [111] orientation, a layer thickness of ~90 nm, and a high transmittance of ≥ 80% have been constructed with the exfoliated and the as-formed nanosheets as building blocks via spin-coating and self-assembly, followed by proper annealing (Fig.…”

“…Solvothermal reaction, however, is needed to extend the nitrate family of 251-LRHs to the bigger ions of Gd, Eu, Nd, and La [16,17]. The work by McIntyre et al [14] [19]. In the latter case, the freezing temperature of ~4 ℃ was shown to be low enough to effectively suppress the thickness growth along the c-axis while high enough to crystallize the hydroxide main layers (the ab planes) [20].…”

Monodisperse colloidal spheres for (Y,Eu)2O3red-emitting phosphors: establishment of processing window and size-dependent luminescence behavior

“…The three groups of excitation peaks at longer wavelengths are the intra-4f electronic transitions of Eu 3+ . Upon UV excitation at 254 nm, the oxide solid solutions exhibit sharp PL lines ranging from 500 to 750 nm, which are associated with the transitions from the 5 D 0 to 7 F J (J = 0, 1, 2, 3, 4) states of Eu 3+ [4], [10][11][12], [15][16][17]. The red emission at 613 nm originates from the hypersensitive 5 D 0 → 7 F 2 forced electric dipole transition.…”