Hydrothermal synthesis and luminescent properties of LnPO4:Tb (Ln = La, Gd) phosphors under VUV excitation

https://doi.org/10.1016/j.jallcom.2006.07.056Get rights and content

Abstract

Tb doped LnPO4 (Ln = La, Gd) phosphors with monoclinic system were successfully prepared by mild hydrothermal reaction at 240 °C. The 543 nm emission of Tb3+ in GdPO4 is higher than in LaPO4. By comparison, it is found that the intensity of host absorption band of GdPO4:Tb is higher than that of LaPO4:Tb which is ascribed to the energy transfer efficiency between the PO43− molecule and Tb3+ is higher. The emission intensity of optimal composition of GdPO4:0.3Tb is comparable with that of commercial Zn2SiO4:0.04Mn phosphor. These results suggest that GdPO4:0.3Tb is a potential candidate for plasma display panels (PDPs) application.

Introduction

Tricolor phosphors for plasma display panels (PDPs) are hot research points in recent years [1], [2], [3]. Been excited by vacuum ultraviolet ray (VUV) in PDPs, few phosphors applied in lamp are feasible to be applied in PDPs. Zn2SiO4:Mn is well known as a good green-emitting phosphor for PDP [4], [5]. However, the decay time of Zn2SiO4:Mn is long. Using the extended Huckel method, Saito et al. [6] calculated energy of the tetrahedral PO43− molecule. According to their results, the lowest energies of the transitions of 2t2  2a, 3t2 are found to exist at 7–10 eV (177–124 nm). The PDPs excitation source (147 nm) is in the range. Therefore, it can be concluded that orthophosphate would be a potential phosphor host. Rao and Devine [7] have realized red, blue and green emissions in rare-earth orthophosphate by doping Eu3+, Tm3+ and Tb3+, respectively. Jung and Lee [8] tried to modify the luminance property of LaPO4:Tb particles by adding some manganese as a co-activator. But under the excitation of VUV (147 nm), the doping Mn is not helpful to improve the photoluminescence intensity of LaPO4:Tb particles. So, Tb doped orthophosphate can be a new candidate to replace Zn2SiO4:Mn. Usually, the rare-earth orthophosphate are prepared by solid state reaction [9], precipitation method [10], spray pyrolysis [11] and hydrothermal means [12]. Up to now, the excitation and emission properties in VUV range of Tb doped rare-earth phosphate prepared by hydrothermal method is scarcely reported. So in this work, we choose the hydrothermal method to synthesis Tb doped LaPO4 and GdPO4 phosphors. Meanwhile, the excitation and the emission properties of the resulted phosphors and the dependence of emission properties on the Tb3+ concentration in LaPO4 and GdPO4 are investigated.

Section snippets

Experimental procedure

The starting materials are Gd2O3 (99.99%), La2O3 (99.99%), Tb4O7 (99.99%) and (NH4)2HPO4 (A.R.). Stoichiometric amount of each oxides are dissolved in diluted nitric by heating. (NH4)2HPO4 is dissolved and added into the former clear solution. Then the mixture is transferred into a Teflon-lined stainless steel autoclave with a filling capacity of 40%. The hydrothermal reaction lasts 6 h at 240 °C.

The crystal structure of samples is characterized by X-ray powder diffraction operating at 40 kV/60 mA,

Results and discussion

The XRD patterns of La0.85Tb0.15PO4 (LT15) and Gd0.85Tb0.15PO4 (GT15) are shown in Fig. 1. The LT15 and GT15 phosphors prepared by hydrothermal reaction at a relative low temperature in our work are monoclinc and they need not further high temperature calcinations as solid state reaction, precipitation method and spray pyrolysis do. It suggests that the hydrothermal reaction is an effective and cost-saving method to prepare phosphors. But the XRD pattern of GT15 is somewhat different from that

Conclusion

  • (1)

    Mild hydrothermal reaction is an effective method to prepare phosphate phosphors for PDPs.

  • (2)

    By comparison, as for Tb doped rare earth orthophosphate phosphor for PDPs, GdPO4 is a better host matrix than LaPO4 because the quenching concentration and the green emission intensity of Tb in GdPO4 are higher than that of LaPO4.

  • (3)

    The brightness of Gd0.7Tb0.3PO4 is higher than that of commercial Zn2SiO4:0.4Mn phosphor. Therefore, Gd0.7Tb0.3PO4 can be used as a green-emitting phosphor for PDPs.

Acknowledgements

This work was supported by Program for New Century Excellent Talents in University of China (NCET, 04-0978), the Key Science Research Project of Ministry of Education of China (105170) and Specialized Research Fund for the Doctoral Program of Higher Education of China (SRFDP, 20040730019).

References (20)

  • H.-C. Lu et al.

    J. Electron Spectrosc. Relat. Phenom.

    (2005)
  • K.Y. Jung et al.

    J. Lumin.

    (2005)
  • C.-H. Kim et al.

    J. Alloy. Compd.

    (2000)
  • R.P. Rao et al.

    J. Lumin.

    (2000)
  • R.P. Rao

    J. Lumin.

    (2005)
  • X. Wu et al.

    Mater. Res. Bull.

    (2002)
  • L.X. Yu et al.

    Solid Stat. Commun.

    (2005)
  • E. Nakazawa et al.

    J. Lumin.

    (1977)
  • W. Di et al.

    Opt. Mater.

    (2005)
  • H. You et al.

    Mater. Sci. Eng.

    (2001)
There are more references available in the full text version of this article.

Cited by (32)

  • Luminescence characteristics and energy transfer of CaSnO<inf>3</inf>:Pr<sup>3+</sup>, Bi<sup>3+</sup> phosphors

    2021, Optik
    Citation Excerpt :

    For instance, the emission spectrum was dominated by red emission (606 nm) in KSr4(BO3)3:Pr3+, blue emission (488 nm) in Gd3Ga3Al2O12:Pr3+ and near-infrared emission in MgGeO3:Pr3+ [6]. In addition, Bi3+ ions have a strong absorption capacity in the vacuum ultraviolet/ultraviolet (VUV/UV) region due to the 1S0 → 3P1 transition and show a wide emission band [7]. Many studies have reported that Bi3+ ions can absorb excitation energy and transfer it to other ions, such as CaS:Bi3+, Tm3+, Dy3+, Ca2YSbO6:Bi3+, Eu3+, Sr4Al14O25:Bi3+, Sm3+, Ba3Y3O9:Bi3+, and Eu3+.

  • UV and VUV induced luminescence in Tb<sup>3+</sup> doped Ca<inf>3</inf>La<inf>3</inf>(BO<inf>3</inf>)<inf>5</inf> phosphors for PDP applications

    2021, Optik
    Citation Excerpt :

    Zn2SiO4:Mn2+ is the most commonly used green phosphor for PDPs, but its long decay time makes it unfavorable for display devices, which has focused efforts on finding new green-emitting phosphors [5]. Recently, alternatives to Zn2SiO4:Mn2+ phosphor were discovered in the form of Tb3+-doped hosts that are capable of absorbing efficiently in the VUV region [6,7]. Borates form an important class of host materials for PDP applications due to their strong absorption in the VUV region [8–10], chemical stability and ease of synthesis [11,12].

  • First-principles study of the optical properties of YPO<inf>4</inf> crystal with oxygen vacancies

    2018, Journal of Physics and Chemistry of Solids
    Citation Excerpt :

    The absorption peak for the F+ center was at 153 nm and this was also close to the experimental value of 152 nm. Zhang et al. [17] and Wu et al. [18] concluded that the absorption bands were located in the 142 nm and 152 nm regions because of the PO43− tetrahedron. According to our simulation calculation, we predicted that the absorption peak at 140 nm was due to the F center and the absorption peak at 152 nm was due to the F+ center.

  • VUV photoluminescence of green-emitting GdPO<inf>4</inf>:Tb,M (M: Al, Zn) synthesized by ultrasonic spray pyrolysis

    2013, Materials Chemistry and Physics
    Citation Excerpt :

    Broad bands are observed at 125–170 nm. This could be attributed to the overlap of the charge transfer (CT) transition of Tb3+ and the host absorption band of (PO4) [17–22]. In addition to the bands, four bands corresponding to the splitting of 7D and 9D configurations in the 5d14f7 excited level of Tb3+ are detected over 170 nm [23].

  • Hydrothermal synthesis and luminescent properties of NaLa(MoO <inf>4</inf>)<inf>2</inf>:Eu<sup>3+</sup>,Tb<sup>3+</sup> phosphors

    2013, Journal of Alloys and Compounds
    Citation Excerpt :

    Therefore, it is desirable to develop environmental friendly, facile, and low-cost methods for the fabrication of inorganic micro-/nanostructures without any organic solvent, catalyst, or surfactant. Recently, much research effort has been directed towards the synthesis of rare-earth compounds since they can be used as highly efficient phosphors, catalysts, and other functional materials by virtue of their novel optical, electronic, and chemical properties [12–14]. In particular, rare-earth molybdate comprise a large class of inorganic compounds that exhibit interesting physical properties and thus have technological applications in the fields of catalysis and optics [15,16].

View all citing articles on Scopus
View full text