Solid-solution formation between arsenic and antimony oxides
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I.
INTRODUCTION
THE question of whether arsenic and antimony oxides form solid solutions stemmed from a study directed at separating the two oxides, tq The experiments and thermodynamic analysis undertaken in that study indicated that this question is central to the viability of a number of proposed separation techniques. The two systems of interest are Sb203-AszO3 and Sb:O4-As203, and the properties of the various polymorphs of these oxides are summarized in Table I. A survey of the literature revealed that there has been no conclusive identification of anhydrous solid antimony/arsenic oxide solid solutions or mixed oxide solid compounds. Hanawalt e t al. 12j claimed to have identified antimony arsenate (SbAsO4) and antimony arsenite (SbAsO3) but provided no details on preparation, composition, or crystal structure. Wretbald, t31 interpreting the work of Trzebiatowski and Bryjak[4] on As-Sb alloys, argued that a solid-solution phase of arsenic and antimony trioxide had formed in their experiments, a claim subsequently rejected by Trzebiatowski. tS] It is known that the trioxide forms of arsenic and antimony form mixed oxide vapor compounds 16'71 and glasses, tSm The potential solid-solution phases that could form between the various polymorphs of arsenic trioxide, antimony trioxide, or antimony tetroxide are as follows: As203 (cubic)/Sb203 (cubic) As203 (cubic)/Sb203 (orthorhombic) AszO3 (monoclinic)/Sb203 (orthorhombic) As203 (monoclinic)/Sb203 (cubic) As203 (cubic)/Sb204 (orthorhombic) AszOs (monoclinic)/SbzO4 (orthorhombic) As203 (cubic)/fl-Sb204 (monoclinic) As203. (monoclinic)/fl-Sb204 (monoclinic) Phases involving cubic antimony trioxide are important in terms of their relevance to separating the oxides, because this trioxide's stability range (900 -7.50 Pna21 a = 0.5436 b = 0.4810 c = 1.176
not known 278 457 3.89 Fd3m a = 1.10778
-312 457 4.23 P21/n a = 0.5339 b = 1.2984 c = 0.45405 /3 = 94.26 deg 18.000 deg, 25 (1, 1,0) 25.772 deg, 50 ( - 1 , 1 , 1) 26.538 deg, 20 ( - 1,3,0) 26.765 deg, 18 (1,0, 1) 27.463 deg, 100 (0, 4, 0) 32.279 deg, 35 (1,4, 1) 39.782 deg, 25 (0,0,2)
Crystal Structure Transition temperature (~ Melting point (~ Boiling point (~ Specific gravity Space group Lattice parameter(s) (nm)
Major peaks (20) 20 intensity (h,k,l)
Physical Data for Arsenic and Antimony Oxides f~9'221
550 to 577 --5.20 Fd3m a = 1.1152
-656 1425 5.79 Pccn a =- 0.4914 b = 1.2468 c = 0.5421
13.739 deg, 10 (1, 1, 1) 27.698 deg, 100 (2,2,2) 32.077 deg, 40 (4, 0, 0) 45.985 deg, 42 (4,4,0) 54.546 deg, 35 (6, 2, 2) 57.128 deg, 11 (4,4,4) 74.063 deg, 12 (6,6,2)
19.403 deg, (1, 1,0) 25.472 deg, (1, 1, 1) 28.382 deg, (1,3,0) 28.382 deg, (1,2, 1) 28.605 deg, (0, 4, 0) 33.796 deg, (0, 1,2) 50.535 deg, (1,6, 1)
Table II.
18
25.840 deg, (1, 1, l) 29.033 deg, (1, 1,2) 30.356 deg, (0, 0, 4) 33.783 deg, (1, 1,3) 48.873 deg, (0, 2, 4) 51.252 deg, (2,2, 1) 53.110 deg, (2,2,2)
25 20 100 75 13 20
Ion
Ionic Radius (nm)
Oxide Bond Length (nm)
As
+3
0.058
0.180
O
II.
+3
0.076
0.200
+5
0.062
0.197
-2
0.132
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