Crystal growth of actinide dioxides by chemical transport

HAL Id: jpa-00218830

https://hal.archives-ouvertes.fr/jpa-00218830

Submitted on 1 Jan 1979

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Crystal growth of actinide dioxides by chemical transport

J. Spirlet, E. Bednarczyk, I. Ray, W. Müller

To cite this version:

J. Spirlet, E. Bednarczyk, I. Ray, W. Müller. Crystal growth of actinide dioxides by chemical transport.

Journal de Physique Colloques, 1979, 40 (C4), pp.C4-108-C4-110. �10.1051/jphyscol:1979434�. �jpa-

00218830�

JOURNAL DE PHYSIQUE Colloque C4, supplément au n° 4, Tome 40, avril 1979, page C4-108

Crystal growth of actinide dioxides by chemical transport

J. C. Spirlet, E . B e d n a r c z y k , I. R a y and W . Miiller

Commission of the European Communities, Joint Research Centre, European Institute for Transuranium Elements, Postfach 22 66, D-7500 Karlsruhe 1, F.R.G.

Résumé. — Des monocristaux de dioxydes d'actinides (U, Np) ont été préparés par la méthode de transport chimique en phase gazeuse, utilisant le tétrachlorure de tellure comme agent de transport. La réaction de transport est réalisée dans des cellules de quartz scellées sous vide et placées dans un four à gradient de température entre 1 075 C et 975 C. Les monocristaux obtenus ont des dimensions comprises entre le mm et le cm. Les oxydes ont été identifiés et caractérisés par les méthodes de Debye-Scherrer et de Weissenberg.

Abstract. — Actinide (U, Np) dioxide single crystals were grown by a chemical transport reaction using tellurium tetrachloride as transporting agent. The oxides were transported from 1 075 to 975 °C in vacuum sealed quartz bulbs. Single crystal sizes were in the mm to cm range. The oxides were identified and characterized by the Debye-Scherrer and Weissenberg methods.

1. Introduction. — T h e c h e m i c a l t r a n s p o r t r e a c - t i o n m e t h o d with TeCl4 a s t r a n s p o r t i n g agent is widely u s e d t o g r o w crystals of a large n u m b e r of r e f r a c t o r y oxides (Table I). This m e t h o d allows t h e p r e p a r a t i o n of crystals u p t o s o m e c m in size with well f o r m e d natural faces a n d with low defect d e n s i t y .

A c t i n i d e dioxide single c r y s t a l s a r e r e q u i r e d for solid s t a t e investigations s u c h a s n e u t r o n diffraction a n d optical reflectivity. L a r g e single crystal faces a r e a l s o suitable for t h e e l e c t r o n i c p r o p e r t i e s s t u d y b y p h o t o e l e c t r o n s p e c t r o s c o p y .

T h e successful p r e p a r a t i o n of large a n d good quality crystals of u r a n i u m dioxide [ 1 , 2 ] e n c o u r a g -

e d u s t o e x t e n d this m e t h o d t o o t h e r actinide d i o x i d e s .

T h e m e c h a n i s m of t h e chemical t r a n s p o r t with TeCl4 as d e s c r i b e d in e q u a t i o n (1) is generally a c c e p t e d for t h e t r a n s p o r t of T i 02, Z r 02, H f 02 [ I ] .

1 0 7 5 °C

M e 02 + TeCl2 + C12 ^ MeCl4 + T e 02 . (I)

• " ⁸ 9 7 5 »C ^s "

F o r o t h e r o x i d e s , including t h o s e of t h e a c t i n i d e s , t h e t r a n s p o r t m e c h a n i s m is c o m p l i c a t e d b y t h e p r e - s e n c e of s t a b l e oxichlorides MeO.,Cly.

2. Experimental. — T h e t r a n s p o r t r e a c t i o n is carried o u t in a q u a r t z b u l b (25 m m in d i a m e t e r ,

T a b l e I. — Summary of the oxide crystal growth experiments by transport with TeCl4.

Oxide T i 02

Ti407

N b 02

H f 02

Z r 02

M o 02

R u 02

R e 02

wo

2 I r 02

O s 02

vo

2 V203

NiFe204

F e203

uo

2

Starting materials 1.5gTi02

5.2mgTeCl4/ml Ti3Os

N b 02

H f 02

Z r 02

M o 02

R u 02

R e 02

wo

2 I r 0² O s 02

vo

2

v²o³

Fe203

+ NiO Fe203

uo

2

uo

2

Bulbs, dimensions

mm 0 / 1 12/100 10/110 —

10/110 10/11

15/150 15/200 200/100

20/100 10/110 30/230

Temperature

°C 1 100/900 1 020/920 1 100/900

1 100/900 1 100/1 000

1 100/900 1000/900 1040/900 980/880

980/920 1 100/900 1 050/950

Growth rate mg/h

2

— 1.5 1 4 30 10 7 22 3.5 2.5 10-20

4 9

6 14 50

Crystal size mm 1 5 x 2 x 2 10 x l x l

2 x 1 x 1

1 5 x 8 x 4 6 x 3 x 2

4 3 1 0 x 4 x 3

7 x 7 x 2 4

8 5 x 5 x 5 30 x 5 x 5

Crystal habit prisms

— prisms

prisms prisms rhombohedra octahedra prisms prisms octahedra

polyhedra prisms prisms

References [1,3]

[4,5]

[1,6,7]

[1]

[ 1 , 8 , 9 , 10,11]

[10, 12]

[13]

[14]

[1]

[2]

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979434

CRYSTAL GROWTH OF ACTINIDE DIOXIDES BY CHEMICAL TRANSPORT C4-109 150 mm long) in a temperature gradient furnace

mounted in a glove box.

Sintered pellets of the starting oxide (10-20 g) are introduced into the carefully cleaned bulb (HNO,, detergent, distilled water). The bulb is evacuated and sealed under a vacuum of tom with a plasma torch.

The number of nucleation centres in the crystalli- zation zone due to the possible presence of oxide traces on the walls is reduced by heating this zone to 1050 "C for 12 hours. The crystals are grown at 975 "C maintaining the oxide feed at 1 075 "C for 2 weeks (Fig. 1).

Fig. 1. - Temperature profile in the furnace during the growth of UOz single crystals.

3. Results.

-

The results of the growth experi- ments of UO,, NpO, single crystals are summarized in table 11. The transporting rate of the oxides is about 20 mg/h. By careful nucleation control, large

Fig. 2.

-

UO1 single crystals in the quartz bulb.

single crystals (up to 1

>!

0.5 X 0.5 cm) are obtained

Fig. 3.

-

Np02 single crystals.

(UO,, Fig. 2). Poor nucleation control results in a large number of small crystals (1-3 mm3, NpO,, Fig. 3). The most commonly found crystal habits for UO, are large prisms, platelets and octahedra. For NpO,, small cubes were obtained (Fig. 4).

The lattice parameters measured by the Debye- Scherrer and the Weissenberg methods are in good agreement with the literature values.

Table 11.

-

Results of the growth experiments.

-

-

Feed quantity (g) 15 5

Transported quantity (g) 8 4.8

Time (d) 15 10

Transporting speed (mg/h) 22 20 Lattice parameter measured 5.470 5.434

literature 5.468 5.434 Dimensions (cm) 1 x 0.5 x 0.5 0.1 x 0.1 x 0.1

Crystal habit prisms cubes

octahedra Fig. 4.

-

Scanning electron micrograph of NpOz single crystals.

References [I] OPPERMANN, H., RITSCHEL, M., Krist. Tech. 10 (1975) 485.

[2] FAILE, S., J. Cryst. Growth 43 (1978) 133.

[3] NIEMYSKI, T., PIEKARCZYK, W., J. Cryst. Growth 1 (1967) 177.

[4] MERCIER, J., SINCE, J., FOURCOUDOT, G., DUMAS, J., DEVE- NYL, J., J. Cryst. Growth 42 (1977) 583.

[5] SINCE, J., AHMED, S., MERCIER, J., J. Cryst. Growth 40 (1977) 301.

[6] KODOMA, H., GOTO, M., J. Cryst. Growth 29 (1975) 77.

[7] SAKATA, T., SAKATA, K., HOFER, G., J. Cryst. Growth 12 (1972) 88.

[8] OPPERMANN, H., REICHELT, W., WOLF, E., J. Cryst. Growth 31 (1975) 49.

[9] OPPERMANN, H., REICHELT, W., KRABBES, G., WOLF,'E..

Krist. Tech. 12 (1977) 717.

[lo] NAGASAWA, K . , BANDO, Y., TAKADA, T., J. Cryst. Growth 17 (1972) 143.

[ I l l LAUNAY, J. C., VILLENEUVE, G., POUCHARD, M., Mat. Res.

Bull. 8 (1973) 997.

[12] LAUNAY, J. C., POUCHARD, M., AYROLES, R., J. Cryst.

Growth 36 (1976) 297.

1131 PESHEV, P., TOSHEV, A , , J. Mat. Sci Lett. 13 (1978) 143.

[I41 PESHEV, P., TOSHEV, A,, J. Mat. Sci. Lett. 11 (1976) 1759.