- Email: [email protected]
Cr3+ induced nucleation and luminescence in silicate glasses
Journal of Luminescence 31 & 32(1984)345-347 North-Holland, Amsterdam
345
3~INDUCED NUCLEATION AND LUMINESCENCE IN SILICATE GLASSES
Cr
Bernard CHAMPAGNON, Frederic DURVILLE, Eugene DUVAL and Georges BOULON Physicochimie des Materiaux Luminescents, U.A. 442 du CNRS, Universite Lyon I, 69622 Vflleurbanne, France Microcrystallites of chromium spinels are developped in silicate glasses by heat treatment. Site distribution and inhomogeneous broadening are studied by laser spectroscopy techniques. 1. INTRODUCTION Nucleation in cordierite glass (52 % Si0 2, 34.7 % A1203, 12.5 % MgO) with 0.8 % of Cr203 has been studied by different techniques notably Small Angle Neutron Scattering ~ (SANS), Small Angle X Ray Scattering (SAXS), Electron Microscopy
~,
E.P.R. and laser spectroscopy. This paper presents the
results obtained by laser spectroscopy. Scattering 3~ions techniques information on particle sizes. Nucleation is of when give the glass is heated above 800°C.Small particles induced by Cr 40 A diameter were observed by SANS and SAXS after 2h of heating at 850°C. The size increases with the time. Characterization of particles after heat treatments at 900°Cshowed that the number of particles is fixed after the first stage of nucleation 1 [P.R. spectra 2 showed that nucleation begins with a concentration of Cr3~ions and continues with dilution of chromium in MgAl 2O4 spinel micro-crystal 1 ites 2. LUMINESCENCE Figure 1 shows the luminescence spectra of different samples following laser excitation (580 nm) at 4.2 K. For non-treated samples (Figure la) the spectrum is composed of4Ttwo bands one is very broad and peaks near 900 nm, it is due 4A to the 2E—÷4A 2—+ 2 transition, the other at 692 nm is narrower and is attributed to the 2transition. The presence of these two bands even at low temperature is usual in the oxide glasses. They comeby from the wideions. distribution of 3+ ion is surrounded six oxygen emitting sites where a Cr ~SANS measurements have been carried out at I.L.L. Grenoble France in collaboration with A. Wright ; SAXS and electron microscopy at INSA Lyon with C. Mai and G. Vigier. 0022—2313/84/$03.OO© Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
346
B.(ianrpag?IQSI £1 a/./(r~)+ m/l,rcL/ ,ilsr/ratHn am! llrr1rjrrr~mmm/mm
4h at 875~Cand then heated for 2h at 900C, only the broad band appeared
)s~~58Omm
(Figure ib). It is not surprising that 2E~4A the 2 for singi e Cr ions disappeared, because it was found from 3+ . [PRWhen experiments the sample thatwasCr pretreated ions are for coupled by an exchange or surper-
PM cu~ofl rJ.,Ixl .
(c)
—
exchange interaction. Under 600 nm excitation, the time-resolved spectra between 1 ms and 3 ms after the excitation showedaband at 775 nm (Figure Ed). The long life-time (~lms) and the wavelength indicate that this
—
1x40 (ci)
emission comes from strongly coupled Cr 636 692 ions and confirm the EPR results. Heat-treatment at 950~Cgives rise to in MgAl a strong3~ions line atare692mainly nm which indicates that Cr 2O 4 microcrystals. However on figure ic 3+ the near I.R. broad band due to Cr ions in glass is more intense than in the
775 Figure 1
900
mm
[missionspectra of cordierite glass (a) without heat—treatment (b) heat-treatment 4h 875CC + 2h 900CC (c) heat-treatment 10 sin 950CC (d) I.R.S. of (b) delay lms gate 3ms
3+ 3+ concentration in Cr the glass non-treated sample. A radiative energy transfer occurs between ions can in niicrocrystals and the glass.(concentration A drop in the quenching). Cr also enhance this emission This can be related to 3+ . . 3 recent works on Cr ions in other glasses 3. FLUORESCENCE LINE NARROWING (FLN)
The line at 692 nm ascribed to the 2[~ 4A 2 transition is rather broad (250 cm~). However it is not very much broader than the same line for a polycrystalline sample of MgA12O4 doped with 1 of Cr203. This large inhomogeneous width reflects a wide distribution of sites due to a partial inversion of spinel 4A FLN of the 2[ ~ 2 line at 160 K allowed us to observe the splitting of the 2[ level by crystal field of axial symmetry, the mean value of which is 70 cm’. Experiment showed that the satellite lines are much broader than the narrow line in resonance with the excitation. This means multiplicity 2E that level,thei.e. on the of sites is reflected not only on the position of the octahedral crystal field, but on the splitting too i.e. on the axial crystal field.
3~induced nucleation and luminescence
347
B. Champagnon et al. / Cr
F.L.N. at very low temperatures (2K - 4K) enabled us to observe the splitting (2D parameter) of the 4A 2 ground
II
state. The splitting varies between with 1 and changes 0.95 excitation cm’ and 1.35 cm inhomogeneous line. the of the
_________
T 4 2K =
T=2.2K
Figure 2 shows the inhomogeneous splitting of the 4A
~
level and the decrease in the sublevel as the
4A 2j
To conclude
.
~
this research illustrates
the importance of laser spectroscopy in the characterization in glasses and also asofa microcrystallites technique to
FIGURE 2 3+ Every inlevels ions MgA1 and F.L.N. of Cr 2O4 spinel microcrystals.
probe the evolution of the luminescence after the glass has been heated. REFERENCES 1) F. DURVILLE, B. CHAMPAGNON, E. DUVAL, G. BOULON, F. GAUME, A.F. WRIGHT and F.N. FITCH, Physics Chem. Glasses to be published (1984). 2) F. DURVILLE, B. CHAMPAGNON, E. DUVAL, G. BOULON, Phys. and Chem. of solids to be published. 3) L.J. ANDREWS, B.C. McCOLLUN1, S.M. STONE and A. LEMPICKI, l6lth Electro— chemical Society Meeting Montréal (May 1982). 4) W. MIKENDA and A. PREISINGER, 11. Lumin. 26 (1981) 53 and (1981) 67.
345
3~INDUCED NUCLEATION AND LUMINESCENCE IN SILICATE GLASSES
Cr
Bernard CHAMPAGNON, Frederic DURVILLE, Eugene DUVAL and Georges BOULON Physicochimie des Materiaux Luminescents, U.A. 442 du CNRS, Universite Lyon I, 69622 Vflleurbanne, France Microcrystallites of chromium spinels are developped in silicate glasses by heat treatment. Site distribution and inhomogeneous broadening are studied by laser spectroscopy techniques. 1. INTRODUCTION Nucleation in cordierite glass (52 % Si0 2, 34.7 % A1203, 12.5 % MgO) with 0.8 % of Cr203 has been studied by different techniques notably Small Angle Neutron Scattering ~ (SANS), Small Angle X Ray Scattering (SAXS), Electron Microscopy
~,
E.P.R. and laser spectroscopy. This paper presents the
results obtained by laser spectroscopy. Scattering 3~ions techniques information on particle sizes. Nucleation is of when give the glass is heated above 800°C.Small particles induced by Cr 40 A diameter were observed by SANS and SAXS after 2h of heating at 850°C. The size increases with the time. Characterization of particles after heat treatments at 900°Cshowed that the number of particles is fixed after the first stage of nucleation 1 [P.R. spectra 2 showed that nucleation begins with a concentration of Cr3~ions and continues with dilution of chromium in MgAl 2O4 spinel micro-crystal 1 ites 2. LUMINESCENCE Figure 1 shows the luminescence spectra of different samples following laser excitation (580 nm) at 4.2 K. For non-treated samples (Figure la) the spectrum is composed of4Ttwo bands one is very broad and peaks near 900 nm, it is due 4A to the 2E—÷4A 2—+ 2 transition, the other at 692 nm is narrower and is attributed to the 2transition. The presence of these two bands even at low temperature is usual in the oxide glasses. They comeby from the wideions. distribution of 3+ ion is surrounded six oxygen emitting sites where a Cr ~SANS measurements have been carried out at I.L.L. Grenoble France in collaboration with A. Wright ; SAXS and electron microscopy at INSA Lyon with C. Mai and G. Vigier. 0022—2313/84/$03.OO© Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
346
B.(ianrpag?IQSI £1 a/./(r~)+ m/l,rcL/ ,ilsr/ratHn am! llrr1rjrrr~mmm/mm
4h at 875~Cand then heated for 2h at 900C, only the broad band appeared
)s~~58Omm
(Figure ib). It is not surprising that 2E~4A the 2 for singi e Cr ions disappeared, because it was found from 3+ . [PRWhen experiments the sample thatwasCr pretreated ions are for coupled by an exchange or surper-
PM cu~ofl rJ.,Ixl .
(c)
—
exchange interaction. Under 600 nm excitation, the time-resolved spectra between 1 ms and 3 ms after the excitation showedaband at 775 nm (Figure Ed). The long life-time (~lms) and the wavelength indicate that this
—
1x40 (ci)
emission comes from strongly coupled Cr 636 692 ions and confirm the EPR results. Heat-treatment at 950~Cgives rise to in MgAl a strong3~ions line atare692mainly nm which indicates that Cr 2O 4 microcrystals. However on figure ic 3+ the near I.R. broad band due to Cr ions in glass is more intense than in the
775 Figure 1
900
mm
[missionspectra of cordierite glass (a) without heat—treatment (b) heat-treatment 4h 875CC + 2h 900CC (c) heat-treatment 10 sin 950CC (d) I.R.S. of (b) delay lms gate 3ms
3+ 3+ concentration in Cr the glass non-treated sample. A radiative energy transfer occurs between ions can in niicrocrystals and the glass.(concentration A drop in the quenching). Cr also enhance this emission This can be related to 3+ . . 3 recent works on Cr ions in other glasses 3. FLUORESCENCE LINE NARROWING (FLN)
The line at 692 nm ascribed to the 2[~ 4A 2 transition is rather broad (250 cm~). However it is not very much broader than the same line for a polycrystalline sample of MgA12O4 doped with 1 of Cr203. This large inhomogeneous width reflects a wide distribution of sites due to a partial inversion of spinel 4A FLN of the 2[ ~ 2 line at 160 K allowed us to observe the splitting of the 2[ level by crystal field of axial symmetry, the mean value of which is 70 cm’. Experiment showed that the satellite lines are much broader than the narrow line in resonance with the excitation. This means multiplicity 2E that level,thei.e. on the of sites is reflected not only on the position of the octahedral crystal field, but on the splitting too i.e. on the axial crystal field.
3~induced nucleation and luminescence
347
B. Champagnon et al. / Cr
F.L.N. at very low temperatures (2K - 4K) enabled us to observe the splitting (2D parameter) of the 4A 2 ground
II
state. The splitting varies between with 1 and changes 0.95 excitation cm’ and 1.35 cm inhomogeneous line. the of the
_________
T 4 2K =
T=2.2K
Figure 2 shows the inhomogeneous splitting of the 4A
~
level and the decrease in the sublevel as the
4A 2j
To conclude
.
~
this research illustrates
the importance of laser spectroscopy in the characterization in glasses and also asofa microcrystallites technique to
FIGURE 2 3+ Every inlevels ions MgA1 and F.L.N. of Cr 2O4 spinel microcrystals.
probe the evolution of the luminescence after the glass has been heated. REFERENCES 1) F. DURVILLE, B. CHAMPAGNON, E. DUVAL, G. BOULON, F. GAUME, A.F. WRIGHT and F.N. FITCH, Physics Chem. Glasses to be published (1984). 2) F. DURVILLE, B. CHAMPAGNON, E. DUVAL, G. BOULON, Phys. and Chem. of solids to be published. 3) L.J. ANDREWS, B.C. McCOLLUN1, S.M. STONE and A. LEMPICKI, l6lth Electro— chemical Society Meeting Montréal (May 1982). 4) W. MIKENDA and A. PREISINGER, 11. Lumin. 26 (1981) 53 and (1981) 67.