Synthesis and luminescent properties of LaPO4:Eu3+ microspheres

doi:10.1016/j.mseb.2013.03.017

Materials Science and Engineering: B

Volume 178, Issue 11, 20 June 2013, Pages 807-810

https://doi.org/10.1016/j.mseb.2013.03.017 Get rights and content

Highlights

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LaPO₄:Eu³⁺ microspheres with a monoclinic phase were synthesized.
•
CTAB plays an important role in the formation of LaPO₄:Eu³⁺ microspheres.
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The LaPO₄:Eu³⁺ microspheres have an enhanced emission intensity.

Abstract

LaPO₄:Eu³⁺ microspheres were synthesized, using LaCl₃, EuCl₃ and (NH₄)₂HPO₄ as starting materials. The morphology, formation mechanism, and luminescent property of samples were systemically studied. X-ray diffraction (XRD) and infrared spectroscopy (IR) show that LaPO₄:Eu³⁺ microspheres have a pure monoclinic phase. Cetyltrimethyl ammonium bromide (CTAB) usually forms spherical micelles above a critical micelle concentration, which plays an important role in the formation of LaPO₄:Eu³⁺ microspheres. The excitation spectrum of LaPO₄:Eu³⁺ microspheres consists of several sharp lines due to the direct excitation of the Eu³⁺ cations from the ground state to higher levels of the 4f-manifold. The emission intensity of microspheres is higher than irregular particles because of the lowlier surface area. The lifetimes of Eu³⁺ ions in the LaPO₄:Eu³⁺ microspheres are determined to be 2.41 ms.

Introduction

For almost half of a century, rare earth (RE)-based phosphors have by far been the most important luminescent materials with application in many technological fields [1], [2], [3]. Recent investigations proved that LnPO₄ (Ln = Y, La, Gd, Lu) phosphors are promising candidates for backlit LCD displays, plasma display panels (PDPS), field emission displays, new generation fluorescent lamps, and so on [4], [5], [6], [7]. Hence, rare earth phosphates in general and lanthanum phosphate in particular have been realized as very potential materials over the years. The LaPO₄:Eu³⁺ phosphors are found to be one of the most familiar red emitting phosphors, and have been successfully explored for the design of luminescent devices [8].

It is well known that the intrinsic properties of inorganic materials are determined by their sizes, shapes, morphologies, compositions, and crystallinity [9], [10]. The phosphor particles with spherical shape are able to increase the screen brightness and improve the resolution [11] because of lower scattering of evolved light and higher packing densities than irregularly shaped particles obtained by conventional solid-state route. In recent years, LaPO₄:Eu³⁺ [8], [12], [13], [14], [15], [16], [17], [18], [19], [20] nanoparticles and microparticles with different morphologies were synthesized by different methods, including LaPO₄:Eu³⁺ microsized hollow and core/shell spheres [21], [22], [23]. To our best knowledge, there are few reports on the synthesis of LaPO₄:Eu³⁺ solid microspheres [24] as well as corresponding optical properties. Therefore, it is desirable to explore feasible, easily controllable, and highly repeatable methods for the synthesis of LaPO₄:Eu³⁺ solid microspheres.

In this paper, we report a surfactant-assisted approach for the synthesis of LaPO₄:Eu³⁺ solid microspheres. The morphology, formation mechanism, and luminescent property of samples were systemically studied.

Section snippets

Experimental

It is known that the accumulation of nitrates in water will cause environmental problems like eutrophication [25]. For reducing the impact caused by disposal of effluents produced during the synthesis processes, one option is certainly use of lanthanum chloride.

All chemicals were of analytic grade purity and were directly used without any treatment. In a typical synthesis, an aqueous solution of 0.2 mol L⁻¹ LaCl₃ and EuCl₃ (lanthanide ion molar ratio La³⁺/Eu³⁺ = 0.95: 0.05) was mixed under vigorous

Results and discussions

Fig. 1 shows the XRD patterns of the as-prepared samples with a molar ratio of La³⁺:Eu³⁺:PO₄³⁻ = 0.95:0.05:1.0. When samples were heat treated at 700 °C, the diffraction peaks are readily indexed to a pure monoclinic type [space group P2₁/n (14)] of LaPO₄ (JCPDS, 84-0600). The doped Eu³⁺ ions do not induce any significant phase change. Obviously, microspheres have higher crystallinity than irregular particles.

The IR spectrum of the microspheres is shown in Fig. 2. It had been reported that the PO₄

Conclusions

LaPO₄:Eu³⁺ microspheres with a monoclinic phase can be synthesized by the presented experiments. CTAB plays an important role in the formation of LaPO₄:Eu³⁺ microspheres. CTAB usually form spherical micelles above a critical micelle concentration, which induce the formation of LaPO₄:Eu³⁺ microspheres. The spherical morphology can enhance the emission intensity of LaPO₄:Eu³⁺ phosphors. The spherical morphology has higher crystallinity, lower surface area, higher packing density and lower

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Materials Science and Engineering: B

Highlights

Abstract

Introduction

Section snippets

Experimental

Results and discussions

Conclusions

References (32)

Materials Science and Engineering B: Solid State Materials for Advanced Technology

Journal of Solid State Chemistry

Journal of Alloys and Compounds

Optical Materials

Optical Materials

Chemical Physics Letters

Materials Chemistry and Physics

Materials Chemistry and Physics

Journal of Rare Earths

Materials Research Bulletin

Journal of Alloys and Compounds

Journal of Colloid and Interface Science

Spectrochimica Acta

Colloids and Surfaces A

Inorganica Chimica Acta

Journal of Luminescence

Cited by (96)

Review on rare earth metals doped LaPO<inf>4</inf> for optoelectronic applications

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Luminescence investigation of lanthanum ions (Eu<sup>3+</sup> or Tb<sup>3+</sup>) doped SrLaGa<inf>3</inf>O<inf>7</inf> fluorescent powders

Efficient removal of phosphate with La modified rGO/silica large-mesoporous films

Ultra-violet B emitting Gd<sup>3+</sup> doped LaP<inf>3</inf>O<inf>9</inf> phosphors prepared by co-precipitation procedure

Short communicationSynthesis and luminescent properties of LaPO4:Eu3+ microspheres

Highlights

Abstract

Introduction

Section snippets

Experimental

Results and discussions

Conclusions

Materials Science and Engineering B: Solid State Materials for Advanced Technology

Journal of Solid State Chemistry

Journal of Alloys and Compounds

Optical Materials

Optical Materials

Chemical Physics Letters

Materials Chemistry and Physics

Materials Chemistry and Physics

Journal of Rare Earths

Materials Research Bulletin

Journal of Alloys and Compounds

Journal of Colloid and Interface Science

Spectrochimica Acta

Colloids and Surfaces A

Inorganica Chimica Acta

Journal of Luminescence

Short communication
Synthesis and luminescent properties of LaPO₄:Eu³⁺ microspheres