Luminescence characteristics of undoped and Eu‐doped GdCa₄O(BO₃)₃ single crystals and nanopowders

Abstract

Single crystals of GdCa 4 O(BO 3 ) 3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% were grown by the Czochralski and micropulling-down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu 3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu 2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol-gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd 3+ at about 312 nm, whereas this emission dramatically decreases in Eu-doped crystals upon X-ray excitation, as well as in Eu-doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125-333 nm for Eu-doped samples leads to strong emission in red coming from the 5 D 0 multiplet of Eu 3+, only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu-doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd 3+ 6 P 7/2 multiplet is 2.79 ms. The Eu 3+ 5 D 0 decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu 3+ luminescence in the 160-200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd 3+-O 2-charge transfer was not observed in crystal obtained by the micropulling-down method.

Luminescence of Eu3+/Gd3+ co-doped silicate sol–gel powders

“…Higher band's intensity was obtained for 7 F 0 -5 L 6 transition of Eu 3 þ ions and this effect is consistent with the results obtained for other systems presented in literature, for example: CsGd 2 F 7 : [22]. In contrast to our results, in GdCa 4 O(BO 3 ) 3 :Eu 3 þ powder system the excitation on 5 D 2 level of Eu 3 þ ions was registered with higher band's intensity compared to the 7 F 0 -5 L 6 transition of Eu 3 þ ions [21,24].…”

“…This research can create more efficient red emitters based on Gd/Eu systems. In the literature there are many publications on the preparation of co-doped Eu/Gd materials, for example: LiGdF 4, GdF 3 , NaGdF 4 , CsGd 2 F 7 , BaF 2 , BaGd 2 ZnO 5 , and K 5 Li 2 GdF 10 [8,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], but only a few papers are available on the sol-gel synthesis of powders [8,14,[18][19][20][21][22]. In recent literature there are no reports on luminescence properties of obtained materials during direct excitation of Eu 3 þ or Gd 3 þ ions and through energy migration Gd 3 þ -Eu 3 þ process.…”

Strong f‐f Excitation and Bright Red Emission in Cd4Gd1‐xEuxO(BO3)3 (0≤x≤1): Near‐UV LED Pumped Red Phosphor with Low Thermal Quenching

“…[27] It crystallizes in the polar space group Cm and possesses an outstanding NLO property,e specially that Yb 3 + or Nd 3 + doped samples may be good candidates fors elf-doubling frequencyl aser crystals. [28,29] The Eu 3 + photoluminescence (PL) was extensively studied in this series of borates, [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] howevert he CT absorption was much stronger than the f-f absorptions and it quenched at al ow concentration (8 %) in Ca 4 GdO(BO 3 ) 3 . [32] In 2010, its analogue Cd 4 BiO(BO 3 ) 3 was reported to show as econd-harmonic generation (SHG) response about 6t imes that of KH 2 PO4 (KDP).…”

Flux Synthesis, Monoclinic Structure, and Luminescence of Europium(III)‐Doped K3La(PO4)2

“…Phosphates containing rare earth metals have been the subjects of intensive structural and spectroscopic studies due to their significant optical properties and possible application as materials for scintillators, light convertors, luminescent hosts, and lasers . Among the advantages of the luminescent materials based on phosphate hosts are low sintering temperature, high luminous efficiency, and high stability .…”