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Deuterides of Nb-Ta, Nb-V and Ta-V solid solutions
Journal of the Less-Common Metals, 119 (1986) 127 - 139
127
DEUTERIDES OF Nb-Ta, N b - V AND T a - V SOLID SOLUTIONS K. WEYMANNand HORST MULLER Institute of Inorganic and Analytical Chemistry, Section Radiochemlstry, University of Freiburg, Albertstrasse 21, D-7800 Freiburg im Breisgau (F.R.G.) (Received August 22, 1985)
Summary The lattice parameters of MD~. 1 (M - Nb, Ta), MD~ 2 (M - Nb, V) and of the monodeuterides and dideuterides of Nb0.6aTa0.~, Nb0.s0V0.s0 and Ta0.s0V0.s0 have been determined and compared with the lattice parameters o f the respective hydride phases. The deuterides have a smaller volume per metal atom than the hydrides, the difference being 1.6% or less. No fundamental dissimilarities between the structures of hydride and deuteride phases were found.
1. Introduction The hydride and deuteride systems o f vanadium, niobium and tantalum are very well known [1]. In continuation of our preceding work on hydrides o f N b - T a [2], N b - V and T a - V [3] alloys we t h o u g h t it worthwhile to compare the lattice parameters of some of the hydride phases with the corresponding deuteride phases which are not known even for the pure metals with one exception, VD~: [4]. Our main interest was directed to the more hydrogen-rich phases MD~I and MD~2 and their alloys, therefore we did not expect t h a t dissimilarities similar to those occurring with the vanadium hydrides and deuterides in the region VH(D)0.7.0.9 (cf. ref. 3, Fig. 1) would be found in our investigation.
2. Experimental methods Uptake of deuterium by cathodic charging was performed in a closed apparatus to prevent contamination of D20 by H20 (see Fig. 1). A funnelshaped electrolysis vessel was used with the consequence that particles attached to ascending gas bubbles were sliding back again to the gold cathode winning electrical contact when the bubbles disappeared at the surface. The anode chamber was dipping into the cathode tray. The electrolyte in the anode chamber had to be changed twice a week. We used 75% DaPO4 as the 0022-5088/86/$3.50
© Elsevier Sequoia/Printed in The Netherlands
128
Fig. 1. Apparatus for cathodic deuteriding of finely divided metals: 1, exsiccator; 2, bubble counter with dibutyl phthalate; 3, electric contact; 4, graphite anode; 5, frittedglass crucible with cap; 6, rubber ring; 7, gold wire; 8, electrolyte; 9, gold sheet with metal sample; 10, PVC tray in PVC beaker with cap.
electrolyte which was prepared from P2Os (pro analysi) and D20 (purity, better than 99.95%, Merck, Darmstadt). The applied voltage was 6 V at the beginning of each experiment; it was increased gradually to 30 V in the following days because of decreasing conductivity owing to the loss of D20 from the electrolyte. The current was decreasing from 250 to 10 mA and the temperature was below 35 °C. Other experimental methods used were described in our previous work [2,3]. 3. Results and discussion
Table 1 shows the results for the deuterides of the three metals and the alloys investigated. Hardcastle and Gibb [4] found 427 pm for the f.c.c. vanadium dihydride phase. Hydride and deuteride phases are compared in Table 2. All deuteride samples prepared have structures analogous to the corresponding hydrides. While the c parameters of the orthorhombic monohydrides of niobium, tantalum and Nb-Ta36.8% increase when hydrogen is substituted by deuterium, all other parameters decrease. The Volume per metal atom, however, decreases for all samples investigated.
129
TABLE 1 Lattice parameters of deuterides
M e t a l or
x in
Monodeuteride
m i x e d crystal
MD x
Structure
a, b, c (pro)
V
Nb
Ta
(Nb-Ta 36.8)
(Nb-V
50.2)
(Ta-V 50.0)
1.92 1.95 2.00 1.60
---f.c.o,
1.89
f.c.o,
0.89
f.c.o,
0.93
f.c.o,
1.08
f.c.o,
1.93
f.c.o.
1.96 1.91 2.01 1.16 1.90
-b.c.c, -b.c.c, b.c.c,
--a, 4 8 3 . 0 b, 4 9 1 . 2 c, 3 4 7 . 2 a, 4 8 3 . 6 b, 4 9 0 . 7 c, 3 4 7 . 2 a, 4 7 8 . 6 b, 4 8 3 . 0 c, 3 4 6 . 4 a, 479.1 b, 4 8 3 . 1 c, 3 4 6 . 8 a, 4 8 1 . 4 b, 4 8 4 . 8 c, 3 4 7 . 1 Not determined a, 331.5 -a, 3 2 9 . 9 a, 3 2 9 . 9
Dideuteride (f.c.c.) ,a ( p m )
Period o f electrolysis
425.8 426.0 426.0 455.4
19 19 11 6
455.4
19 d
h h d d
6d
13d
452.7
4 d
453.0
11 d
453.4 442.4 442.6 436.8 437.1
14 1 10 1 12
d d d d d
TABLE 2 Lattice parameters and volume per metal atom and relative reduction of volume per metal atom
of comparable
hydrides and deuterides
Lattice parameters (pm) V o l u m e p e r m e t a l a t o m ( 1 0 6 p m 3)
Vanadium MH~ 2 hydrogen poor MH~ 2 hydrogen rich Niobium MH~I hydrogen rich
Hydride
Deuteride
a = 426.7 V' = 19.42 a = 427.5 V' = 19.53
a = 425.8 V r = 19.30 a = 426.0 V' = 19.33
a = 484.3 b = 491.7
a = 483.0 b = 491.2
--~v'/v' (%)
0.6 1.0
(con tinued)
130 T A B L E 2 (continued)
Lattice parameters ( p r o ) Volume per metal atom ( 1 0 6 p m a)
MH~2 hydrogen poor Tantalum M H ~ l h y d r o g e n rich
( N b - T a 36.8 ) MH~.I h y d r o g e n r i c h
MH~ 2 hydrogen poor M H ~ 2 h y d r o g e n rich (Nb-V 50.2) MH~.I h y d r o g e n r i c h MH~2 hydrogen poor M H ~ 2 h y d r o g e n rich (Ta-V 50.0) M H ~ I h y d r o g e n rich MH~2 hydrogen poor MH~2 h y d r o g e n rich
Hydride
Deuteride
c = 346.7 V ' -- 2 0 . 6 4 a -- 4 5 6 . 2 V' = 23.74
c = 347.2 V' = 20.59 a = 455.4 V' = 23.61
a = 479.6 b = 483.8 c = 346.1 V' = 20.08
a = 479.1 b = 483.1 c = 346.8 V' = 20.06
a = 482.6 b = 488.6 c = 346.4 V' = 20.42 a = 453.9 V' = 23.38 a = 454.6 V' = 23.49
a = 481.4 b = 484.8 c -- 3 4 7 . 1 V' = 20.25 a = 452.7 V' = 23.19 a = 453.4 V' = 23.30
a -- 3 3 1 . 6 V' = 18.23 a = 442.9 V t = 21.72 a = 443.5 V ~= 21.81
a = 331.5 V r = 18.21 a = 442.4 V' = 21.65 a = 442.6 V p= 21.68
a = 330.0 V' = 17.97 a = 437.6 V' = 20.95 a = 439.4 V' = 21.21
a = 329.9 V' = 1 7 . 9 5 a = 436.8 V' = 20.83 a = 437.1 V r = 20.88
- A v ' / v ' (%)
0.2 0.5
0.1
0.8 0.8 0.8
0.1 0.3 0.6
0.1 0.6 1.6
Acknowledgments This schaft.
investigation
The
82 computer
numerical
was
supported
calculations
at the University
by
the
Deutsche
were performed
Forschungsgemein-
using the UNIVAC
of Freiburg.
References 1 T. S c h o b e r a n d H. Wenzl, Top. Appl. Phys., 29 ( 1 9 7 8 ) 11. 2 H. Miiller, K. W e y m a n n a n d P. H a r t w i g , J. Less-Common Met., 74 ( 1 9 8 0 ) 17.
3 H. Mfiller and K. Weymann, J. Less-Common Met., 119 (1986) 115. 4 K. I. H a r d c a s t l e a n d T. R. P. G i b b , J. Phys. Chem., 76 ( 1 9 7 2 ) 9 2 7 .
1100/
127
DEUTERIDES OF Nb-Ta, N b - V AND T a - V SOLID SOLUTIONS K. WEYMANNand HORST MULLER Institute of Inorganic and Analytical Chemistry, Section Radiochemlstry, University of Freiburg, Albertstrasse 21, D-7800 Freiburg im Breisgau (F.R.G.) (Received August 22, 1985)
Summary The lattice parameters of MD~. 1 (M - Nb, Ta), MD~ 2 (M - Nb, V) and of the monodeuterides and dideuterides of Nb0.6aTa0.~, Nb0.s0V0.s0 and Ta0.s0V0.s0 have been determined and compared with the lattice parameters o f the respective hydride phases. The deuterides have a smaller volume per metal atom than the hydrides, the difference being 1.6% or less. No fundamental dissimilarities between the structures of hydride and deuteride phases were found.
1. Introduction The hydride and deuteride systems o f vanadium, niobium and tantalum are very well known [1]. In continuation of our preceding work on hydrides o f N b - T a [2], N b - V and T a - V [3] alloys we t h o u g h t it worthwhile to compare the lattice parameters of some of the hydride phases with the corresponding deuteride phases which are not known even for the pure metals with one exception, VD~: [4]. Our main interest was directed to the more hydrogen-rich phases MD~I and MD~2 and their alloys, therefore we did not expect t h a t dissimilarities similar to those occurring with the vanadium hydrides and deuterides in the region VH(D)0.7.0.9 (cf. ref. 3, Fig. 1) would be found in our investigation.
2. Experimental methods Uptake of deuterium by cathodic charging was performed in a closed apparatus to prevent contamination of D20 by H20 (see Fig. 1). A funnelshaped electrolysis vessel was used with the consequence that particles attached to ascending gas bubbles were sliding back again to the gold cathode winning electrical contact when the bubbles disappeared at the surface. The anode chamber was dipping into the cathode tray. The electrolyte in the anode chamber had to be changed twice a week. We used 75% DaPO4 as the 0022-5088/86/$3.50
© Elsevier Sequoia/Printed in The Netherlands
128
Fig. 1. Apparatus for cathodic deuteriding of finely divided metals: 1, exsiccator; 2, bubble counter with dibutyl phthalate; 3, electric contact; 4, graphite anode; 5, frittedglass crucible with cap; 6, rubber ring; 7, gold wire; 8, electrolyte; 9, gold sheet with metal sample; 10, PVC tray in PVC beaker with cap.
electrolyte which was prepared from P2Os (pro analysi) and D20 (purity, better than 99.95%, Merck, Darmstadt). The applied voltage was 6 V at the beginning of each experiment; it was increased gradually to 30 V in the following days because of decreasing conductivity owing to the loss of D20 from the electrolyte. The current was decreasing from 250 to 10 mA and the temperature was below 35 °C. Other experimental methods used were described in our previous work [2,3]. 3. Results and discussion
Table 1 shows the results for the deuterides of the three metals and the alloys investigated. Hardcastle and Gibb [4] found 427 pm for the f.c.c. vanadium dihydride phase. Hydride and deuteride phases are compared in Table 2. All deuteride samples prepared have structures analogous to the corresponding hydrides. While the c parameters of the orthorhombic monohydrides of niobium, tantalum and Nb-Ta36.8% increase when hydrogen is substituted by deuterium, all other parameters decrease. The Volume per metal atom, however, decreases for all samples investigated.
129
TABLE 1 Lattice parameters of deuterides
M e t a l or
x in
Monodeuteride
m i x e d crystal
MD x
Structure
a, b, c (pro)
V
Nb
Ta
(Nb-Ta 36.8)
(Nb-V
50.2)
(Ta-V 50.0)
1.92 1.95 2.00 1.60
---f.c.o,
1.89
f.c.o,
0.89
f.c.o,
0.93
f.c.o,
1.08
f.c.o,
1.93
f.c.o.
1.96 1.91 2.01 1.16 1.90
-b.c.c, -b.c.c, b.c.c,
--a, 4 8 3 . 0 b, 4 9 1 . 2 c, 3 4 7 . 2 a, 4 8 3 . 6 b, 4 9 0 . 7 c, 3 4 7 . 2 a, 4 7 8 . 6 b, 4 8 3 . 0 c, 3 4 6 . 4 a, 479.1 b, 4 8 3 . 1 c, 3 4 6 . 8 a, 4 8 1 . 4 b, 4 8 4 . 8 c, 3 4 7 . 1 Not determined a, 331.5 -a, 3 2 9 . 9 a, 3 2 9 . 9
Dideuteride (f.c.c.) ,a ( p m )
Period o f electrolysis
425.8 426.0 426.0 455.4
19 19 11 6
455.4
19 d
h h d d
6d
13d
452.7
4 d
453.0
11 d
453.4 442.4 442.6 436.8 437.1
14 1 10 1 12
d d d d d
TABLE 2 Lattice parameters and volume per metal atom and relative reduction of volume per metal atom
of comparable
hydrides and deuterides
Lattice parameters (pm) V o l u m e p e r m e t a l a t o m ( 1 0 6 p m 3)
Vanadium MH~ 2 hydrogen poor MH~ 2 hydrogen rich Niobium MH~I hydrogen rich
Hydride
Deuteride
a = 426.7 V' = 19.42 a = 427.5 V' = 19.53
a = 425.8 V r = 19.30 a = 426.0 V' = 19.33
a = 484.3 b = 491.7
a = 483.0 b = 491.2
--~v'/v' (%)
0.6 1.0
(con tinued)
130 T A B L E 2 (continued)
Lattice parameters ( p r o ) Volume per metal atom ( 1 0 6 p m a)
MH~2 hydrogen poor Tantalum M H ~ l h y d r o g e n rich
( N b - T a 36.8 ) MH~.I h y d r o g e n r i c h
MH~ 2 hydrogen poor M H ~ 2 h y d r o g e n rich (Nb-V 50.2) MH~.I h y d r o g e n r i c h MH~2 hydrogen poor M H ~ 2 h y d r o g e n rich (Ta-V 50.0) M H ~ I h y d r o g e n rich MH~2 hydrogen poor MH~2 h y d r o g e n rich
Hydride
Deuteride
c = 346.7 V ' -- 2 0 . 6 4 a -- 4 5 6 . 2 V' = 23.74
c = 347.2 V' = 20.59 a = 455.4 V' = 23.61
a = 479.6 b = 483.8 c = 346.1 V' = 20.08
a = 479.1 b = 483.1 c = 346.8 V' = 20.06
a = 482.6 b = 488.6 c = 346.4 V' = 20.42 a = 453.9 V' = 23.38 a = 454.6 V' = 23.49
a = 481.4 b = 484.8 c -- 3 4 7 . 1 V' = 20.25 a = 452.7 V' = 23.19 a = 453.4 V' = 23.30
a -- 3 3 1 . 6 V' = 18.23 a = 442.9 V t = 21.72 a = 443.5 V ~= 21.81
a = 331.5 V r = 18.21 a = 442.4 V' = 21.65 a = 442.6 V p= 21.68
a = 330.0 V' = 17.97 a = 437.6 V' = 20.95 a = 439.4 V' = 21.21
a = 329.9 V' = 1 7 . 9 5 a = 436.8 V' = 20.83 a = 437.1 V r = 20.88
- A v ' / v ' (%)
0.2 0.5
0.1
0.8 0.8 0.8
0.1 0.3 0.6
0.1 0.6 1.6
Acknowledgments This schaft.
investigation
The
82 computer
numerical
was
supported
calculations
at the University
by
the
Deutsche
were performed
Forschungsgemein-
using the UNIVAC
of Freiburg.
References 1 T. S c h o b e r a n d H. Wenzl, Top. Appl. Phys., 29 ( 1 9 7 8 ) 11. 2 H. Miiller, K. W e y m a n n a n d P. H a r t w i g , J. Less-Common Met., 74 ( 1 9 8 0 ) 17.
3 H. Mfiller and K. Weymann, J. Less-Common Met., 119 (1986) 115. 4 K. I. H a r d c a s t l e a n d T. R. P. G i b b , J. Phys. Chem., 76 ( 1 9 7 2 ) 9 2 7 .
1100/