Purification of rare earth metals by electromigration - application examples

(1) metal electrically purity cerium Ce purified transition metal taken from the molten salt electrolysis can reach 99.8%, impurities are mainly iron, oxygen, carbon, and molybdenum. The metal crucible was re-melted to a length of about 160 mm and a rod having a diameter of about 13 mm. Then, in a sealed device with inert gas protection, the two ends are clamped on the water-cooled electrode head, and a direct current of 120V and 500A is applied to heat the metal crucible to (600±10) ° C (about less than the melting point of the crucible). 200 ° C), the results of long-term electromigration refining are shown in Table 1. Practice has shown that the effective migration of carbon impurities takes about 100h, while the iron is about 50h.
            Table 2 Contents of impurities in metal ruthenium before and after electromigration refining Unit: μg/g
Impurity element
a uniform rod before refining
Middle section of the rod after refining
Impurity element
a uniform rod before refining
Middle section of the rod after refining
C
O 2
Fe
Cu
Mo
400
50
1300
120
400
140
350
30
40
440
Al
Ca
Mg
Si
500
20
10
250
200
10
40
70
(2) Electromigration purification of other rare earth metals Due to the difference in melting point, electrical conductivity, and U/D value of each rare earth metal, the process conditions required for electromigration are also different. Table 2 lists electromigration. yttrium, gadolinium, terbium, lutetium, neodymium, process conditions and purification effect.
Table 2 Process conditions and purification effects of electromigration purification of rare earth metals
element
atmosphere
Temperature / °C
Time / h
Original test bar impurity content (μg / g)
Impurity content after purification (μg/g)
C
N
O
C
N
O
Y
Y
Gd
Gd
Tb
Lu
Nd
Argon
1.3×10 -5 Pa
Helium
Ultra high vacuum
Ultra high vacuum
Ultra high vacuum
Ultra high vacuum
1370
1175
1245
1100
1050
1150
860
200
190
150
310
350
168
1237
-
100
twenty three
1000
-
70
13
510
10
28
4
30
15
54
3330
25
81
500
380
475
45
-
120
2
8
-
60
-
75
8
0.5
15
6
1
340
60
6
11
25
42
16

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