Template-Free Hydrothermal Synthesis and Luminescent Properties of Octahedral NaGd(MoO[sub 4])[sub 2]:Eu[sup 3+] Microcrystals

Abstract

Uniform and well-crystallized octahedral NaGd(MoO4)2:Eu3+ microcrystals have been successfully synthesized by a facile one-step hydrothermal synthesis method without involving any templates. The prepared samples were systematically characterized by powder X-ray diffraction, field-emission-scanning electron microscopy, photoluminescence (PL), and photoluminescent excitation spectra. The starting pH value played an important role in the pure-phase formation and uniform morphology of octahedral microcrystals. Detailed proofs indicated that the growth process of NaGd(MoO4)2:Eu3+ microcrystals was dominated by a nucleation–crystallization-oriented attachment mechanism. Furthermore, the luminescent properties of the as-synthesized NaGd(MoO4)2:Eu3+ microcrystals were investigated, demonstrating that the PL intensity was influenced by the different morphologies, and the bipyramidal octahedra NaGd(MoO4)2:Eu3+ luminescent microcrystals might be applied as an excellent red component for near-UV white light emitting diodes.

Synthesis of Red‐Emitting AgGd0.9Eu0.1(MoO4)2 Phosphors by Precipitation at Room Temperature

“…The excitation spectrum of fluorescent AgGd 0.9 Eu 0.1 (MoO 4 ) 2 prepared using the precipitant NH 3 ÁH 2 O [ Fig. 16 The sharp peaks are assigned to f-f transitions of Eu 3+ , which are dominated by the excitation of 7 F 0 ? The spectrum consists of a broad intense band (200-350 nm) centered at 274 nm attributed to O 2À -Mo 6+ and O 2À -Eu 3+ charge-transfer (C-T) transitions, 10,15 and a number of sharp peaks at lower energy between 350 and 560 nm.…”

“…The spectrum consists of a broad intense band (200-350 nm) centered at 274 nm attributed to O 2À -Mo 6+ and O 2À -Eu 3+ charge-transfer (C-T) transitions, 10,15 and a number of sharp peaks at lower energy between 350 and 560 nm. 16 The sharp peaks are assigned to f-f transitions of Eu 3+ , which are dominated by the excitation of 7 F 0 ? 5 L 6 and 7 F 0 ?…”

Tuning of crystal phase and luminescence properties of Gd2(MoO4)3:Dy3+ phosphors

“…The starting reagents gadolinium nitrate (Gd(NO 3 ) 3 ) and dysprosium nitrate (Dy(NO 3 ) 3 ) solutions were obtained by dissolving gadolinium oxide (99.99%) and dysprosium oxide (99.99%) in dilute nitric acid solution under heating with agitation, respectively. All the other chemicals were analytical grade and used as received without further treatment.…”

“…For the hydrothermal treatment, we used 60 mL Teflon cups. In a typical procedure, according to the nominal composition Gd 2Àx (MoO 4 ) 3 :Dy x 3+ (x = 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20), the stoichiometric mixtures of Gd(NO 3 ) 3 and Dy(NO 3 ) 3 solutions were firstly added into the test tube. Subsequently, a stoichiometric amount of (NH 4 ) 6 Mo 7 O 24 Á4H 2 O solution was added into the above solution with strong magnetic stirring at room temperature for 10 min to form a homogeneous solution.…”

“…The CIE chromaticity coordinates of orthorhombic (a) and monoclinic (b) Gd 2Àx (MoO 4 )3 :Dy x 3+ plotted in the 1931 CIE diagrams (l ex = 389 nm).…”