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Generation of (F+2)AH Centres in Sodium Ion Doped KCl:CO2-3
M. Diaf, I. Chihi, A. Hamaïdia, El. Akrmi
To cite this version:
M. Diaf, I. Chihi, A. Hamaïdia, El. Akrmi. Generation of (F+2)AH Centres in Sodium Ion Doped KCl:CO2-3. Journal de Physique III, EDP Sciences, 1996, 6 (1), pp.1-6. �10.1051/jp3:1996111�. �jpa- 00249441�
J. Phys. III France 6 (1996) 1-6 JANUARY1996, PAGE1
Generation of (F()
AH Centres in Sodiuln Ion Doped KCI:CO(~
M. Diaf, I. Chihi, A. Hamaidia and A. El Akrmi
Institut de Physique, UniversitA d'Annaba, BP. 12, 23000 Annaba, Algeria
(Received 18 July 1995, accepted 16 October 1995)
PACS.61.72Ji Point defects and defect clusters PACS.78.50Ec Insulators
PACS.42.55Rz Other solid state lasers
Abstract. ~Ve demonstrate that (F))AH centres of KCI may be obtained from crystals
doped ~vith K2C03 and Nacl, grown by the Czochralski method in open atmosphere. The optical properties of (F))AH centres thus produced are exactly the same as those of (F))AH
centres prepared by the usual technique, which involves superoxide doping and a controlled
atmosphere.
R4sum4. Nous montrons que Ies centres (F))AH de KCI peuvent Atre obtenus h partir de cristaux dopAs par K2C03 et Nacl, fabriqu4s par la m4thode de Czochralski h I'air Iibre. Les propriAtAs optiques des centres (F))AH ainsi produits sont exactement Ies mimes que celles des centres (F))AH prAparAs par la technique habituelle, qui comporte Ie dopage par un superoxyde
et I'emploi d'une atmosphAre contr6I6e.
1. Introduction
PI like centres in alkali halides played an important role in the development of colour centre
lasers (see, for instance, the review article of Gellermann iii). Promising characteristics of these centres stimulated research in the direction of improving their stability under intense pump light irradiation, by associating them with neighbouring impurities. Thus, PI centres
perturbed by anionic impurities (O~~, S~~) or by the combination oi such impurities with
foreign cations (Li+, Na+), respectively called (Pj)H and (PI)AH centres, have been obtained in Nacl:OH~ [2j, in KCI and KBr:O~~ [3j, in KCI and KBr:O~~ Na+ [4].
On the other hand, doping KCI with potassium superoxide K02 is rather tricky because this very hygroscopic compound is quite rapidly converted into hydroxide in the presence oi air moisture. Moreover, there is a problem oi thermal decomposition oi K02 when crystal growth is performed under an inert atmosphere, without a partial pressure of oxygen. More
recently, (PI)H centres have been obtained in KCI with easily handled dopes: K2C03 IS,6j or KN03 (6,7j.
In the present communication, we shall show that it is possible to creaf,e (PI)H and (PI)AH
centres in KCI:CO(~ and KCI:CO(~ Na+ crystals grown in open atmosphere. In Section 2,
we shall describe sample preparation. Section 3 contains the LNT absorption and emission spectra oi the centres we have obtained. Finally, Section 4 discusses the experimental results.
© Les (ditions d~ Ph,,I(jii~ 1'196
2. Sample preparation
KCI:CO(~ and KCI:CO(~ Na+ crystals have been grown in our laboratory by the Czochralski technique under open atmosphere. ~Ve used pure grade KCI powder from RAachim Company.
K2C03 and Nacl dopes were added in molar proportions oi 1000 to 2000 ppm. In order to obtain successiul doping with K2C03, it is necessary to add it to the melt just beiore starting
the crystal pulling. Room temperature IR absorption spectra in the 200 4000 cm~~ do- main, obtained with an IR PYE UNICAM Ltd spectrophotometer, show a CO(~ ion gradient, increasing irom the seed used for crystal growth.
After cleaving and preliminary polishing, samples approximately 10x10x2 mm have been colored by the sealed bomb method in copper tubes in our laboratory or by the heat-pipe technique [8] at "Laboratoire de Spectroscopie Atomique de Caen" (France). During the cooling back to room temperature aiter coloration, aggregates and even colloids are formed in the
samples, and several annealings to temperatures near 650 °C followed by quenching on a
copper plate are necessary to destroy these aggregates. In order to avoid break oi samples
by too sudden quenching, they are wrapped in thin stainless steel foils during this thermal
processing.
Light irradiations at -10 °C and at LNT are performed by an Osram HBO 100 W high
pressure mercury lamp through a Schott Monochromat 546 filter. The sample is fixed on the cold finger oi a small adjustable temperature cryostat. Absorption and emission spectra at LNT are measured respectively with a Perkin-Elmer Lambda 9 spectrophotometer and with
a Jobin-Yvon HRS 2 monochromator iollowed by a PbS detector and a Staniord Research
System SR 510 phase sensitive amplifier.
3. Absorption and Emission of (Fj)H and (F()AH centres
3.1. (FI)H AND PI CENTRES IN KCL:CO(~ Lifante et al. [5] have suggested that during
additive coloration CO(~ ions decompose according to one of the following reactions:
(CO(~ D) + 2 F - 2 (O~~ D) + CO
or
(CO(~ D) + F (O~~ D) + C02-
O~~ D pairs which are created during the coloration are characterized by an absorption
band at 280 nm.
On the other hand, Raerinne and Ketolainen [7], in spite of the presence of CO(~ ions in their samples, were unable to observe this decomposition either in additive or in electrolytic
coloration. Aiter such colorations, their samples behaved like pure KCI.
We studied samples of KCI:CO(~ grown under open atmosphere at temperatures of about 890 °C. Additive coloration of these samples actually resulted in decomposition oi CO(~ ions.
A sample of KCI doped with 2000 ppm oi CO(~ and additively colored shows after annealing
and quenching a very intense 280 nm band characteristic of O~~ D pairs (Fig. 1), in addition to F band (at 540 nm), F2 band (at 800 nm), a band of unknown origin at 1000 nm and a
very weak absorption around 1.45 /tm due to (PI)H centres already present at this stage of the processing, but in much lower concentration than in Lifante et ai.'s work [5j.
Photoaggregation by the 546 nm line of mercury at 10 °C results in sizeable growth oi the 1.45 /tm band and optical densities of 0.3 can be obtained for a sample thickness of 2 mm,
which is the right order of magnitude for the active sample of a colour centre laser [3]. The location of the absorption band is, within experimental uncertainties, the same as reported in
N°I GENERATION OF (F))AH CENTRES IN SODIUM ION DOPED KCI:CO(~ 3 3.0
2.5
2.0
)~
# l.5
~(
o I,o
2
3 o.5
0 0
200 400 600 800 1000 1200 1400 1600 1800
Wavelength (nm)
Fig. I. Absorption spectra at LNT of KCI:CO(~ l) After annealing; 2) after photoaggregation
with 546 nm light at 10 °C during lo minutes; 3) after subsequent LNT irradiation with 436 nm
light during 10 minutes.
the literature for (FI)H centres (see Tab. I). Moreover, contrarily to other matrices, KCI is known to have only one variety of (FI)H centres [3]. And, in fact, irradiation of our samples with the 436 nm line of mercury at LNT destroys the 1.45 /tm centres and converts them into intrinsic F) centres which absorb at 1.38 /tm. This is another proof of the (Fj)H nature of the centres created in our carbonated crystals.
3. 2. (PI)AH CENTRES IN KCL: CO(~ NA+ The LNT absorption spectrum oi an additively
colored KCI:CO(~.Na+ sample proves once again that decomposition of CO(~ molecular ions takes place. The 280 nm absorption band oi O~~ D pairs in KCI:CO(~ is shifted to 269 nm
when the crystal is codoped with sodium, a displacement which is similar to the one reported by Wandt and Gellermann [4j, but a little smaller (-11 nm instead oi 15). This 269 nm
band is assigned to O~~ D pairs perturbed by neighbouring Na+ ions.
After annealing at 650 °C and quenching at room temperature on a copper plate, we perform photoaggregation at -10 °C by the 546 nm line of the mercury HBO lamp and we thus create, with an optical density of 0.33 for 2 mm thickness, an absorption band which peaks at 1298 nm at LNT (Fig. 2), assigned to a first variety of (Fj)AH centres, which was called la) variety by El Akrmi et al. [9j, by analogy with the la) variety oi (Fj)H centres [3j. Excitation by a white lamp through an 1.3 /tm interierence filter gives rise to a fluorescence with a maximum located at 1698 nm (Fig. 3). Variety (a) oi (PI)AH centres is observed to be quite stable thermally in the dark at room temperature, in accordance with previous reports 11,4,9j.
On the other hand, (FI)AH (a) centres are iragile under luminous irradiation. Indeed, by illuminating the sample at LNT by the 436 nm line of a mercury lamp, one reorientates the
(FI)AH centres, converting them from variety (a) into another one which we call 16) (see Tab. I).
The absorption band of (FI)AH 16) centres is centered at 1378 nm, with an optical density
Table I. Absorption and eYnission band YnamYna at LNT for (F/)H and (F~)AH centres m
KGi
Variety (a) Variety (b)
Centre Dope Absorption Emission Emission
(F~+)t~ KO~ 1450 1780 [3]
(F~+)i~ K~CO~ 1454 1780 Present
work
(F~-)w KO~+ 1290 1660 1390 1860 [4]
Nacl
(F~~)~t KO~+ 1295 1698 1379 1896 [9]
Nacl
(F~-)~,j K~CO, + 1298 1698 1378 1896 Present
work
2.5
)~
# l,5
#~ O 1,o
0.5 2
o-o
200 400 600 800 1000 1200 1400 1600 1800
Wavelength (nm)
Fig. 2. Absorption spect.ra at LNT of KCI:CO(~.Na+. I) After photoaggregation wit-h 546 nm
light at 10 °C during 10 minutes; 2) after subsequent LNT ii-radiation with 436 nm light during 10 minutes.
oi 0.3 (Fig. 2). Excitation of this absorption band by 1.3 /tm light produces a fluorescence with its maximum at 1896 nm (Fig. 3). Location of absorption and emission bands of both species la) and (b) are summarized in the table and found to be in very good agreement with those reported by previous authors [4,9j. Thus all observed optical properties indicate that the
centres obtained in KCI:CO(~.Na+ crystals are identical with the laser active (FI)AH centres
first described by Wandt and Gellermann [3j.
N°I GENERATION OF (F))AH CENTRES IN SODIUM ION DOPED KCI:CO(~
0.80
2
( 0.60 C
fi©
I©
f 0.40 0C
0.20
~'~i500 1600 1700 1800 1900 2000 2100 2200
Wavelength (nm)
Fig. 3. Emission spectra at LNT of KCI:CO(~.Na+. I) After photoaggregation with 546 nm light
at 10 °C during 10 minutes; 2) after subsequent LNT irradiation with 436
nm light during lo minutes.
4. Discussion
The present work provides three new pieces of information:
I) It confirms that (F))H centres of KCI can be obtained by using CO(~ (instead oi super-
oxide) doping oi the crystals, which supports the results of reference [5] against those of ref-
erence [7j. Probably the possibility to obtain O~~ ions from CO(~ doping depends critically
on some crystal growth parameter, the nature oi which still remains undetermined: thus, in
apparently very similar conditions, Liiante et al. [5j obtain (F))H centres immediately after additive coloration, we obtain them only aiter subsequent photoaggregation at -10 °C, while Raerinne and I(etolainen iii do not obtain them at all.
ii) It is possible to create (F))AH centres in KCI without using the rather tricky superoxide doping. Indeed, the centres we obtain ivith 1(2C03 and Nacl dopings have exactly the same
optical properties as those prepared with the usual addition of K02 and Nacl [4,9j (Sect. 3.2).
This possibility of obtaining important number densities of (F))AH centres without superoxide doping had been previously demonstrated by Lifante et al. [6j who used N03Na doping; here
we show it to exist also with K2C03 and Nacl dopings, opening the possibility to adjust separately the oxygen and sodium concentrations. This may turn out to be very useful for the
preparation of a i;aluable liser material.
iii) Finally, we have demonstrated that (F))H and (F))AH centres in KCI may be obtained from crystals grown in open air. This was previously known for (F))H centres in Nacl which
can be obtained from OH~ doping [1-3]: thus atmospheric moisture is not a nuisance and may even be useful. But in KCI, (F))H centres are known to be unobtainable in sizeable
concentration from OH~ doping 11,3](~) and previous research wM performed with crystals
grown, under suitably controlled atmosphere, with Up 11,3], CO(~ [5] or NOj [6,7] doping.
Our Czochralski method in open atmosphere is obviously simpler to implement. It would be oi interest to veriiy whether our KCI:CO(~ Na+ crystals work properly as active samples in
colour centre lasers.
Acknowledgments
The spectroscopic measurements (NIR and visible absorption and fluorescence) were performed
at Laboratoire de Spectroscopie Atomique, ERS 137, ISMRA, 14050 Caen, France, in the iramework oi Algerian-French cooperation contract n° 92 MDU 202. We are very thankful to Proiessor Jean Margerie and to Doctor Jean-Louis Doualan of this Laboratory ior their
hospitality, for loan of equipment and for discussion of the results.
References
ill Gellermann W., J. Phys. CheYn. Solids 52 (1991) 249.
[2j Pinto J-F-, Georgiou E. and Pollock C-R-, Stable color-center laser in OH~ doped Nacl
operating in the 1.41-tot.81 /tm region, Opt. Lett. ii (1986) .519.
[3j Wandt D., Gellermann W., Liity F. and Welling H., Tunable cw laser operation in the 1.45-2.16 /tm range based on PI -like centers in Up doped Nacl, KCI and I(Br crystals,
J. Appl. Phys. 61 (1987) 864.
[4j Wandt D. and Gellermann W., Efficient cw color center laser operation in the 1.7 to 2.2 /tm range based on PI like centers in KCI:Na+ Up crystals, Opt. GoYnm. 61 (1987) 405.
[5j Lifante G., Silisten P., Cusso' F. and Jaque F., (F))H- centre production in molecule-
doped KCI, Phys. Stat. Sol. (b) 159 (1990) K 37.
[6] Liiante G., Silfsten P., Cusso' F., Garcia-SolA J., Jaque F. and Henderson B., (F))H-
centers in doped alkali halides, J. L~Yninescence 48 & 49 (1991) 779.
[7] Raerinne P. and Ketolainen P., A method to colour electrolytically oxygen-doped alkali halide crystals, Sol. State GoYnYn. 86 (1993) 699.
[8] Mollenauer L-F-, Apparatus for the coloration of laser-quality alkali halide crystals, Rev.
Sci. Inst. 49 (1978) 809.
[9j El Akrmi A., Ketolainen P., Doualan J-L-, Kawa E., Margerie J. and Rocher B., Spectro- scopic properties of (PI)AH centres in oxygen- and sulfur-doped alkali halides, J. Phys.:
Condensed Matter 6 (1994) 4859.
(~ We have verified this point: KCI crystals grown in open air, under the same experimental conditions
as our other samples, but without K2C03 addition, fail to show any detectable (F))H band after additive coloration and 546 nm irradiation at 10 °C. Thus, the oxygen ion of our (F))H
or (F))AH
centres does come from the carbonate doping and not from the uncontrolled atmosphere under which
the growth was performed.
J. Phys. III France 6 (1996) 7-22 JANUARY 1996, PAGE 7
#tude de la rdpartition des courants de Foucault pulsds dans une
configuration de contr61e non destructif
J.-C. Bour, E. Zubiri, P. Vasseur et A. Billat
Laboratoire d'Applications de la Micro41ectronique, Universit6 de Reims, B-P. 347, 51062 Reims Cedex 2, France
(Regu le 29 mai 1995, rAvisA le 3 octobre 1995, acceptd le 13 octobre 1995)
PACS.07.55+x Magnetic instruments and techniques PACS.41.20-q Electric, magnetic, and electromagnetic fields
PACS.81.70Dw Nondestructive testing
RAsum4. La mise au point d'un dispositif expArimental de contr6Ie par courants de Foucault,
en mode sinusfidal ou impulsionnel, nAcessite l'optimisation d'un certain nombre de paramAtres.
Cette optimisation est gdn4ralement tongue et dAlicate h exAcuter en pratique puisqu'elle rAsulte de plusieurs compromis. L'Atude en simulation prAsentAe ici peut Atre considArAe comme une
aide, plut6t qualitative, puisqu'elle prdcise le comportement des dilfdrents paramAtres impliquds
dans la mise
au point de la recherche expdrimentale de dAfauts. Nous montrons dans un premier temps I'influence de la distance capteur-cible sur la sensibilitA du capteur h dAtecter un dAfaut.
Nous mettons ensuite en 6vidence Ie fait que la gAom6trie du capteur ne peut Atre nAgligAe dans la pratique. Cette constatation nous conduira h dAfinir un rAseau de courbes montrant I'Avolution de la profondeur de pAnAtration en fonction de la durAe de I'impulsion pour dilfArents rayons de
bobines. Nous d4terminerons 4galement la zone de sensibilitA maximale d'une bobine, dans Ie but de localiser prAcisAment Ie dAfaut dAtectA dans la plaque. Enfin nous montrerons que la valeur de la vraie profondeur de pAnAtration est Iide h I'Apaisseur de la plaque m4taIlique examinAe. Ce
r6suItat trAs important devra Agalement Atre pris en compte dans le cas d'un contr61e rAeI.
Abstract. Adjusting an experimental device of control by eddy-currents in sinusoidal or
pulse mode requires the optimization of a certain number of parameters. Generally, the imple-
mentation of the latter operations is long and delicate, since it is issued of many compromises.
The simulation study presented in this paper can be considered as a qualitative help because it
specifies the behaviour of the different parameters implied in the adjustment of the experimental defect research. First, we prove the influence of the lift-off
on the defect detection's sensitivity
of the flat sensor we used. Next we give prominence to the fact, in practice, we cannot disregard
the geometry of the sensor, as we could do in theory. This result will lead us to define a family
of curves showing the evolution of the depth of penetration as a function of the pulse's duration
for different coil radii. We also determine the maximal sensor's sensitivity area, with the aim of locating the defect detected in the plate with precision. Finally,
we prove the dependency
between the true value of the depth of penetration and the thickness of the considered metallic plate. This very important result should equally be taken under consideration in the case of a real control.
1. Introduction
Au nive~u du contr61e non destructif, [es courants de Foucault sont traitAs de deux maniAres diffArentes.
La m4thode la plus utilisAe est celle des Courants de Foucault Sinusoidaux (C.F.S.) dans la- quelle le champ AlectromagnAtique est gAnArA par un courant alternatii. Celle-ci n'est applicable
que pour la recherche de d4fauts surfaciques, ou trAs proches de la suriace 11,2], puisque la densitA des courants induits d4croit sensiblement avec l'4paisseur du matAriau (effet de peau).
La seconde mAthode. avec laquelle nous travaillons, est d4riv4e de la prAc4dente, mais h la diff4rence de celle-ci, le champ 4lectromagnAtique est g4n4r4 par une impulsion de courant,
d'amplitude et de durAe variable. Cette technique appe14e Courants de Foucault Puls4s (C.F.P.)
permet la d4tection de d4iauts situAs h des proiondeurs non accessibles par des courants de Foucault sinusoidaux.
Le travail que nous pr4sentons ici concerne l'4tude de dAiauts (absence de matiAre) dans des plaques d'acier austAnitique. Cet acier. indApendamment du fait qu'il soit trAs utilis4 dans l'industrie nud4aire, ne permet pas l'emploi de mAthodes de contr61e non destructif telles que;
par exemple. la magn4toscopie ou le contr61e par perte de flux [3]. Une bonne maitrise d'un contr61e par courants de Foucault dans ce type de mat4riau est donc une n4cessit4.
L'Atude expArimentale que nous avons men4e pr4alablement [2,4], nous a conduit h d4velopper
un capteur comportant trois bobines (Fig. 1). L'414ment sensible de base que nous utilisons pour constituer le capteur est une bobine plate gravAe en forme de spirale sur un circuit imprim4 double face [5].
Les r4sultats obtenus sont intAressants, mais ils ont montrA une divergence sensible entre [es profondeurs des dAfauts effectivement dAtectAs, et la profondeur de p4nAtration dAfinie
thAoriquement. Cette divergence ne peut Atre entiArement expliquAe par le fait que l'impulsion utilisAe thAoriquement pour le calcul de la profondeur est de iorme diffArente (rectangulaire)
de celle gAnArAe expArimentalement (semi-sinusoidale).
Ces constatations nous ont conduit h entreprendre une simulation dont le but est de mettre
en Avidence [es diffArents iacteurs impliquAs. On sait [6] que la durAe de l'impulsion Amise
a une influence sur la rApartition des courants induits. On peut penser que [es paramAtres gAomAtriques de la bobine Amettrice ne sont pas sans effet sur celle-ci. notamment sun leur
Emettrice
~l'~
Rdceptrices
Fig. I. Capteur utilis6 expArimentalement.
[The driver and pickup coils.]
