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Luminescence of rubidium titanyl phosphate (RbTiOPO4)
Materials Chemistry and Physics, 25 (1990)
537L 539
537
SHORT COMMUNICATION
LUMINESCENCE
G. BLASSE
OF RUBIDIUM
(RbTiOPO,)
Institute,
University
of Utrecht,
P.O. Box 80.000,
3508 TA
(The Netherlands)
L.H. BRIKNER
and A. FERRETTI
E.I. du Pont de Nemours Department, 19880-0356
Received
PHOSPHATE
and G.J. DIRKSEN
Debye Research Utrecht
TITANYL
and Company,
Experimental
Station,
Central
Research
and Development
P.O. Box 80.356, Wilmington,
Delaware,
(USA)
February
13, 1990; accepted
April
9, 1990
ABSTRACT Rubidium
titanyl
temperatures. equal
phosphate
(RbTiOP04)
Due to small structural
shows luminescence
differences
at low
this luminescence
is not
to that of KTiOP04.
INTRODUCTION In recent
years we have reported
(KTP). This compound luminescence
is rather unusual
[3]. This has been delocalisation effects
interesting
Its crystal
(- 0.01 A)
zig-zag
parameters.
structure
with KTP. However,
chains
amount
[1,2]. The
of a related
by Masse
the Ti-0 distances
these
it seemed
compound
with
we choose
and Grenier
are slightly
shift
of
[3.4]. Since
angles,
For this purpose
was reported
of KTiOPO,,
material
due to the small Stokes
and Ti-0-Ti
the luminescence
structure
luminescence optical
a considerable
titanate
on Ti-0 distances
to investigate
(RbTP).
isomorphous
by assuming
in the irregular
different
nonlinear
for a titanate
interpreted
depend markedly
slightly
on the peculiar
is a very promising
RbTiOP04
[5]. RbTP is different
[2,5].
EXPERIMENTAL The RbTiOPO, - rubidium was similar
crystal
fluoride
used
flux containing
to that described
0254~584/90/$3.50
in this study was grown
from a rubidium
phosphate
TiO, and a RbTP seed. The apparatus
for KTP growth
[6]. The melt was cooled
used from
0 ElsevierSequoia/Printedin The Netherlands
538 800
‘C
to
780
“C at
0.2
“C per
hour after which time the crystal was withdrawn
from the melt and slowly cooled to room temperature. The optical measurements were performed as described before [3,4].
RESULTS AND DISCUSSION RbTP shows luminescence at 4.2 K.
The emission band has a maximum at 410 nm,
whereas KTP has this maximum at 390 nm.
On the other hand, the excitation
band of the RbTP emission is at shorter wavelength than in the case of KTP. Therefore the Stokes shift of the RbTP emission is much larger than that of the KTP emission. Table I summarizes these data.
Table I.
Luminescence data at 4.2 K and crystallographicdata at 300 K for RbTiOPO4 and KTiOP04.
Maximum of emission band (nm) Maximum of excitation band (run) Maximum of emission band (cm-') Maximum of excitation band (cm-') Stokes shift (cm-') a (A) b (A) c (A) v (A)
RbTiOPO,
KTiOPO,
410. 320' 23.000. 31.250' J.450n 12.97' 6.4gc 10.58' 890.6'
390b
340b 25.200b 29.400b 4.200b 12.81= 6.40c 10.62c 870.7’
a This work b Ref. 3 c Ref. 5
As has been argued elsewhere [7,8] the larger Stokes shift indicates less delocalisation of the excited state. Undoubtedly this has to be ascribed to the ionic radius of Rb+ which is about 0,l A larger than that of K+ [9]. This is also clear from the crystallographic data reported for comparable crystals (see Table I) [2,5]. In this way the wavefunction overlap between the titanate groups in RbTP will be slightly reduced compared to that in KTP. This has significant consequences, particularly for the Stokes shift of the luminescence. The results observed for RbTP fit, therefore, the model proposed before [3,4].
CONCLUSION RbTP shows a luminescence which is similar to that of KTP. Due to the larger radius of Rb' the Stokes shift is larger.
539
REFERENCES 1
F.C. Zumsteg, J.D. Bierlein and T.E. Gier, L
2
G.D. Stucky, M.L.F. Phillips and T.E. Gier, Chem. Mater., l (1989) 492.
3
G. Blasse. G.J. Dirksen and L.H. Brixner, bat. Res, Bull., 2;e (1985) 989.
4
G. Blasse and L.H. Brixner, Bat. Res. Ml.:
5
R. Masse and J.C. Grenier, Bull. Sot, Er, Mineral. Crist., 94 (1971) 437.
6
P.F. Bordui, J.C. Jacco, G.M. Loiacono, R.A. Stolzenberger and J.J. Zola, L
Crvstal. Growth
u
Phvs.. 47 (1976) 4980
24 (1989) 1099.
84 (1987) 403.
7
L.G.J. de Haart, A.J. de Vries and G. Blasse, J. Solid State Chem., 3
8
G. Blasse, Proeress UJU
9
R.D. Shannon and C.T. Prewitt, &ta
(1985) 291.
m
(1970) 1046; &&B
%.K&
Chem. U
(1988) 79.
Crvst., m
Crvst., A32 (1976) 751.
(1969) 925; Acta Crvst.,
537L 539
537
SHORT COMMUNICATION
LUMINESCENCE
G. BLASSE
OF RUBIDIUM
(RbTiOPO,)
Institute,
University
of Utrecht,
P.O. Box 80.000,
3508 TA
(The Netherlands)
L.H. BRIKNER
and A. FERRETTI
E.I. du Pont de Nemours Department, 19880-0356
Received
PHOSPHATE
and G.J. DIRKSEN
Debye Research Utrecht
TITANYL
and Company,
Experimental
Station,
Central
Research
and Development
P.O. Box 80.356, Wilmington,
Delaware,
(USA)
February
13, 1990; accepted
April
9, 1990
ABSTRACT Rubidium
titanyl
temperatures. equal
phosphate
(RbTiOP04)
Due to small structural
shows luminescence
differences
at low
this luminescence
is not
to that of KTiOP04.
INTRODUCTION In recent
years we have reported
(KTP). This compound luminescence
is rather unusual
[3]. This has been delocalisation effects
interesting
Its crystal
(- 0.01 A)
zig-zag
parameters.
structure
with KTP. However,
chains
amount
[1,2]. The
of a related
by Masse
the Ti-0 distances
these
it seemed
compound
with
we choose
and Grenier
are slightly
shift
of
[3.4]. Since
angles,
For this purpose
was reported
of KTiOPO,,
material
due to the small Stokes
and Ti-0-Ti
the luminescence
structure
luminescence optical
a considerable
titanate
on Ti-0 distances
to investigate
(RbTP).
isomorphous
by assuming
in the irregular
different
nonlinear
for a titanate
interpreted
depend markedly
slightly
on the peculiar
is a very promising
RbTiOP04
[5]. RbTP is different
[2,5].
EXPERIMENTAL The RbTiOPO, - rubidium was similar
crystal
fluoride
used
flux containing
to that described
0254~584/90/$3.50
in this study was grown
from a rubidium
phosphate
TiO, and a RbTP seed. The apparatus
for KTP growth
[6]. The melt was cooled
used from
0 ElsevierSequoia/Printedin The Netherlands
538 800
‘C
to
780
“C at
0.2
“C per
hour after which time the crystal was withdrawn
from the melt and slowly cooled to room temperature. The optical measurements were performed as described before [3,4].
RESULTS AND DISCUSSION RbTP shows luminescence at 4.2 K.
The emission band has a maximum at 410 nm,
whereas KTP has this maximum at 390 nm.
On the other hand, the excitation
band of the RbTP emission is at shorter wavelength than in the case of KTP. Therefore the Stokes shift of the RbTP emission is much larger than that of the KTP emission. Table I summarizes these data.
Table I.
Luminescence data at 4.2 K and crystallographicdata at 300 K for RbTiOPO4 and KTiOP04.
Maximum of emission band (nm) Maximum of excitation band (run) Maximum of emission band (cm-') Maximum of excitation band (cm-') Stokes shift (cm-') a (A) b (A) c (A) v (A)
RbTiOPO,
KTiOPO,
410. 320' 23.000. 31.250' J.450n 12.97' 6.4gc 10.58' 890.6'
390b
340b 25.200b 29.400b 4.200b 12.81= 6.40c 10.62c 870.7’
a This work b Ref. 3 c Ref. 5
As has been argued elsewhere [7,8] the larger Stokes shift indicates less delocalisation of the excited state. Undoubtedly this has to be ascribed to the ionic radius of Rb+ which is about 0,l A larger than that of K+ [9]. This is also clear from the crystallographic data reported for comparable crystals (see Table I) [2,5]. In this way the wavefunction overlap between the titanate groups in RbTP will be slightly reduced compared to that in KTP. This has significant consequences, particularly for the Stokes shift of the luminescence. The results observed for RbTP fit, therefore, the model proposed before [3,4].
CONCLUSION RbTP shows a luminescence which is similar to that of KTP. Due to the larger radius of Rb' the Stokes shift is larger.
539
REFERENCES 1
F.C. Zumsteg, J.D. Bierlein and T.E. Gier, L
2
G.D. Stucky, M.L.F. Phillips and T.E. Gier, Chem. Mater., l (1989) 492.
3
G. Blasse. G.J. Dirksen and L.H. Brixner, bat. Res, Bull., 2;e (1985) 989.
4
G. Blasse and L.H. Brixner, Bat. Res. Ml.:
5
R. Masse and J.C. Grenier, Bull. Sot, Er, Mineral. Crist., 94 (1971) 437.
6
P.F. Bordui, J.C. Jacco, G.M. Loiacono, R.A. Stolzenberger and J.J. Zola, L
Crvstal. Growth
u
Phvs.. 47 (1976) 4980
24 (1989) 1099.
84 (1987) 403.
7
L.G.J. de Haart, A.J. de Vries and G. Blasse, J. Solid State Chem., 3
8
G. Blasse, Proeress UJU
9
R.D. Shannon and C.T. Prewitt, &ta
(1985) 291.
m
(1970) 1046; &&B
%.K&
Chem. U
(1988) 79.
Crvst., m
Crvst., A32 (1976) 751.
(1969) 925; Acta Crvst.,