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Single crystal and film growth of actinide pnictides by chemical vapour transport
G. Calestani, J. Spirlet, W. Müller
To cite this version:
G. Calestani, J. Spirlet, W. Müller. Single crystal and film growth of actinide pnictides by chemical vapour transport. Journal de Physique Colloques, 1979, 40 (C4), pp.C4-106-C4-107.
�10.1051/jphyscol:1979433�. �jpa-00218829�
JOURNAL DE PHYSIQUE Colloque C4, supplément au n° 4, Tome 40, avril 1979, page C4-106
Single crystal and film growth of actinide pnictides by chemical vapour transport
G. C a l e s t a n i , J. C . Spirlet and W . Miiller
Commission of the European Communities, Joint Research Centre, European Institute for Transuranium Elements, Postfach 2266, D-7500 Karlsruhe 1, F.R.G.
Résumé. — Des monocristaux et des couches minces de pnictides (As, Sb) d'actinides (Th, Pa, U) ont été préparés à partir des éléments par transport chimique en phase gazeuse en utilisant l'iode comme agent de transport. Les composés d'actinides sont déposés sur un support de tungstène chauffé par induction haute fréquence suivant le procédé van Arkel. Les températures de déposition sont comprises entre 1 000 et 2 200 °C selon le composé désiré. La température de la cellule de quartz est maintenue entre 400 et 600 °C. Les composés obtenus sont identifiés et caractérisés par diffraction des rayons X (Debye-Scherrer, cristal tournant, Weissenberg).
Abstract. — Single crystals and films of actinide (Th, Pa, U) pnictides (As, Sb) were prepared from the elements, by chemical vapour transport using iodine as transporting agent. In a van Arkel process, the actinide compounds were deposited on an induction-heated tungsten support. Depending on the compounds, deposition temperatures ranged from 1 000 to 2 200 °C, whereas the quartz bulb was kept at 400 to 600 °C. The deposits were identified and characterized by X-ray diffraction (Debye-Scherrer, rotating crystal, Weissenberg) methods.
1. Introduction. — Actinide pnictides a r e p r e p a r - ed b y direct s y n t h e s i s b e t w e e n t h e actinide metal a n d t h e v a p o u r of t h e c o r r e s p o n d i n g p n i c t o g e n a t t e m p e r a t u r e s ranging from 400 t o 1 200 °C [ 1 , 2].
T h e m e t a l / p n i c t o g e n ratio of t h e pnictides is 1:1, 3:4 or 1:2. M o n o p n i c t i d e s of t h e light actinides a r e o b t a i n e d b y r e d u c t i o n of t h e higher pnictides b y t h e actinide metal [1] : c o m p a c t e d pellets of h o m o g e n i z - e d m i x t u r e s a r e r e a c t e d a t t e m p e r a t u r e s b e t w e e n 1 600 a n d 2 200 °C in t u n g s t e n crucibles u n d e r va- c u u m or in an argon a t m o s p h e r e . M o n o n i t r i d e s a n d m o n o p h o s p h i d e s a r e also f o r m e d b y t h e r m a l d e c o m - position of higher c o m p o u n d s in a d y n a m i c v a c u u m . I n g e n e r a l , t h e pnictides a r e o b t a i n e d in p o w d e r f o r m .
Single crystals of t h e higher u r a n i u m a n d n e p t u - n i u m pnictides c a n b e g r o w n b y chemical v a p o u r t r a n s p o r t in sealed q u a r t z b u l b s using iodine as t r a n s p o r t i n g agent [ 1 , 3 , 4 ] . A t t e m p t s t o p r e p a r e t h o r i u m pnictides a n d t h e m o n o p n i c t i d e s of u r a n i u m a n d p r o t a c t i n i u m b y this m e t h o d r e s u l t e d in t h e a t t a c k of t h e q u a r t z wall [ 4 , 5 ] , e v e n at t e m p e r a t u r e s as low a s 800 °C.
I n o r d e r t o p r e p a r e actinide pnictides in c o m p a c t f o r m a s r e q u i r e d for solid s t a t e investigations b u t avoiding possible high t e m p e r a t u r e r e a c t i o n s with t h e wall m a t e r i a l , t h e direct s y n t h e s i s of t h e actinide c o m p o u n d s w a s a t t e m p t e d b y a van A r k e l t y p e p r o c e d u r e : starting f r o m t h e e l e m e n t s a n d in t h e p r e s e n c e of iodine a s t r a n s p o r t i n g agent, t h e pnicti- d e s w e r e t o b e d e p o s i t e d o n a radiof r e q u e n c y h e a t e d t u n g s t e n s u p p o r t (T^) w h e r e a s t h e q u a r t z b u l b w o u l d b e maintained a t a l o w e r t e m p e r a t u r e (Tj).
2. Experimental. — T h e v a n Arkel p r o c e s s is carried out in a n e v a c u a t e d (10~6 torr) q u a r t z b u l b , w h i c h c o n t a i n s t h e (electropolished) t u n g s t e n s u p - p o r t , t h e e l e m e n t s and a q u a r t z capillary with t h e t r a n s p o r t i n g agent (Fig. 1). T h e t e m p e r a t u r e T, d e - t e r m i n e s t h e v a p o u r p r e s s u r e of t h e iodide a n d ,
Fig. 1. — Apparatus for preparation and crystal growth of actini- de pnictides by the van Arkel process.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979433
SINGLE CRYSTAL AND FILM GROWTH OF ACTINIDE PNICTIDES C4-107
together with
T,,
controls the deposition rate at the support. The temperature T2 determines, in addi- tion, the composition of the deposited compound.The temperatures used for the synthesis of va- rious actinide pnictides are summarized in table I.
Table I.
-
Bulb and support temperatures used for the synthesis of the different pnictides.Compound
-
U3As4 U As USb, U3Sb4 USb Th,As4 ThAs ThSb, Th,Sb4 ThSb PaAs, Pa3As4 Pa3Sb,
3. Results.
-
All compounds were obtained as polycrystalline films (Fig. 2) and (with the exception of ThAs) as single crystals (Fig. 3).Fig. 2. -Tungsten support with UAs film and single crystals.
Fig. 3. - Scanning electron micrograph of UAs single crystals.
The pnictides were identified and characterized by X-ray diffraction methods (Debye-Schemer, rotating crystal, Weissenberg). The lattice parameters agree with literature data [ I , 5, 6, 71 ; examples are given in table 11.
Table 11.
-
Crystallographic structure and lattice parameters of the actinide pnictides.Compound Symmetry -
ThAs U As USb ThaAsa U ~ A S ~ Pa,As, PaAs,
- f.c.c.
f.c.c.
f.c.c.
b.c.c.
b.c.c.
b.c.c.
tetragonal Pa,Sba b.c.c.
PaSb, tetragonal
Lattice parameters
A
measured literature Space group [2,6,71
References
[I] CHARVILLAT, J. P., Thtse de doctorat en sciences, Universitk de Clermont-Ferrand (1977).
[2] DELL, R. M., BRIDGER, N. J. in Lanthanides and Actinides, Inorganic Chemistry Series One, edited by H. Emelkus and K. W. Bagnall (Butterworths, London) 7 (1972) 211.
[3] HENKIE, Z., Technologia Monokrysztalow (Polish Scientific Editions, Warsaw) 2 (1974) 56.
[4j BEDNARC~YK, E., SPIRLET, J. C., unpublished results (1976).
[5j HENKIE, Z., MARKOWSKI, P. J., J. Cryst. Growth 41 (1977) 303.
[6j HERY, Y., DAMIEN, D., HAESSLER, M., DE NOVION, C.-H., Radiochem. Radioanal. Lett. 32 (1978) 283.
[7] DELL, R. M., in The Actinides, Comprehensive Inorganic Chemistry, edited by J. C. Bailar (Pergamon Press) 5 (1973) 319.
