INFORMATION O a a .Aoi Chemistry-Traniuranie Elements

INFORMATION O a a .Aoi Chemistry-Traniuranie Elements

INFORMATION o a a .aoi Chemistry-Traniuranie Elements UNIVERSITY O r CALIFORNIA Radiation Laboratory Contract No. W-7405-eng~48 CUBSITIClTIOH CAKCBLUD IV. TT Ftv«Jbs Itti'.s fJ«cR'otsdLisV^ CRYSTAL STRUCTURES OF AMERICIUM COMPOUNDS D. H. Templeton and Carol H. Dauben February 3, 1953 RESTRICTEO^JCTA This document cqpm pLrw ricted data as defined in ttagSrarfic Energy Act of 1944. Its tsn fip rtfa l or disclosure of Its contents ^p*ny manner to an unautor- ised person is prohibited. Berkeley, California UNIVERSITY Of CALIFORNIA Rodiotiofl Loborotory 42RC8 Cover Shoot INDE X NO. Ill K£ ■ -10/ Do not rsrtovt Tbit document eo nto in t__ IL- pages Tbit is copy ^ of tor lot tL Glassification Eoch perton who rtcoivot thltdocument must tipn the cover thstt I Route to Notsd by Date Route to Noted by D aft OHO A im *[|S 5(M) CRYSTAL STRUCTURES OF AMERICIUM COMPOUNDS1 D. H. Templeton and Carol H. Dauben Department of Chemistry and Radiation Laboratory University of California, Berkeley, California February 3, 1953 ABSTRACT The crystal structures of several compounds of americium, element 95, have been determined by the X-ray powder diffraction method. AisF^ is hexagonal (LaF^ type) with a = 4. 067 t 0.001 X and c « 7. 225 t 0.002 Si for the pseudoceil which explains the powder data. AmO^ is cubic (CaF^ type) with 1 a = 5. 38) t 0.001 X AmOCl is tetragonal (PbFCl type) with a = 4.00+O.OlX, c = 6.78 t 0.01 X. The metal parameter la 0.18 t 0.01. Anr^Oj ie cubic when prepared at 600° C. and hexagonal when prepared at 800° C. For the cable form (Mn2?3 ty?e) a = 11.03 t o . 01 X. The metal parameter la -0.030 t 0.002. For the hexagonal form (LajOj type) a = 3.817 t O.OOSX, c = 5 .9 7 1 1 0.010 X. 'Thle reaearch wae performed under the auepicea of the AEC. C O N t^^A L -4- UCRL-21G1 CRYSTAL STRUCTURES OF AMERICIUM COMPOUNDS D. H. Templeton and Carol H. Dauben Department of Chemistry and Radiation Laboratory University of California, Berkeley, California F ebruary 5, 1953 In cooperation with Professor B. B. Cunningham and his students, we have been observing the x-ray diffraction patterna of various compounds of americium, element 95. The isolation of americium produced by the beta decay of Pu*** has been described by Cunningham. * (2) B. B. Cunningham, National Nuclear Energy Series, Plutonium Project Record, Vol. 14B, "The Transuranium Elements: Research Papers,"Paper No. 19.2, McGraw-Hill Book Co., Inc., New York, N. Y ., 1949. Prior to 1948 the purification was usually terminated when the impurities (chiefly lanthanum) were reduced to one or two percent. Since that time there have been available americium stocks of much higher purity. * In this paper we report our results concerning the O) H. R. Lohr and B. B. Cunningham, J. Am. Chem. Soc. 73, 2025-28 (1951). (4) L. Eyring, H. R. Lohr, and B. B. Cunningham, J. Am. Chem. Soc. 74, 1188-90 (1952). ■ ip crystal structures of AmF^, AxnO^, AmOCl, and two forms of Am^Gk^. aB ■ , we***" *§• UCRL-2101 Americium Trlfluorlde Americium trlfluorlde wit prepared by Dr. L. Eyeing 1 1 described elsewhere.* Semple A (Table I) was pink la color, (5) E. G. Westrum and L. Eyrlng, J. Am. Cham, Soc. 73, 3396-98 (1951). like that described by Tried.* Sample B wae a subsequent preparation (6) S. Tried, J. Am. Chem. Soc. 73. 416-18 (1931). which was grey or lavender in color. Its diffraction pattern was almost identical with that of Sample A. Sample C was prepared by Dr. J. C. Wa 11matm from the very pare americium nitrate eolation used by Howland and Calvin for their magnetic Investigation.7 (7) J. J. Howland and M. Calvin, J. Chem. Phys. 18, 239-43 (1950). 8ome of this americium was precipitated as the hydroxide and heated with oxygen to 523° C. It was then heated in hydrogen fluoride to 715° C. The product was pink but after a week, part of It had turned yellow. Sample C consisted of some of this yellow material. With each of the three samples an excellent powder diffraction g pattern was obtained corresponding to the LaT^-type structure. (!) I. Oftedal, Z. physik. Chem. B 5. 272-91 (1929)t B 13, 190-200 U931). Tito unit cell dimensions listed In Table 1 rt(*f to tHo hexagonal peeodo-cell containing two americium atoms. This call accounts for ail tbs diffraction linos observed la tbs powder patterns. Faint reflections in tIngle crystal patterns’8 9 require an a axis which Is (9) We have observed these weak reflections for a tingle crystal of pare synthetic CeF y showing that the effect in tysonite* is not due to ordering between the cerium and lanthanom atoms. /! times as large as those listed in Table L Zacharlaeen10' 11 first (10) W. H. Zacharlaeen, Phye. Rev. 73. U04-5 (1948). (U) W. H. Zacharlaeen, Acta Cryst. 2, 388*90 (1949). obaerved this structure for americium trifluoride and has reported two sets of cell dimensions based on samples of uncertain parity. Hit results (corrected from kX units) are included in the table. Our three templet disagree by only slightly more than the estimated limits of error. Since the material prepared by Wailmann it likely to be of the highest purity, we adopt aa our beet valuee a • 4.007 X and c « 7.225 X for the pseudo-cell. For the larger cell, sj» 7. 044 X. The change from Zacharlesea's values is not sufficient to affect his ionic radius for Am ^, 0.99 X 12 We attach no structural significance to the color (12) W. H. Zacharlaeen, American Crystallographic Association, Abstracts of Meeting, Pennsylvania State College, April 10*12, 1950. changes but attribute them to surface effects of eome kind. - 1 UCRL-2101 Table I Unit Cell Dimensions for Americium Trifluoride Sample c (X) A* 4. 069 t 0.001 7.229 t-0.002 B* 4.069 t 0.001 7.229 t 0.002 C* 4.067 to . 001 7.221 1 0.002 ZacHarlasen10** 4.07$ t 0.002 7. 2)9 t 0.004 Zacharlasen**' * 4.0811 0.002 7.2491 0.004 a Based on Cu K a, X « 1.5418 X. b Corrected from kX units. .8 . UCRL-2101 Americium Dioxide The black americium dioxide was shown by Zachariaeen to have the fluorite type structure. ^ For samplee of uncertain purity, the edge of the cubic unit cell was found to be 5. 372 t 0. 005 kX and 5. 377 t 0. 003 kX. We have examined by x-ray diffraction several americium dioxide samples, three of which were especially well crystallised and gave excellent powder patterns. Sample A (Table 11) was prepared by Dr. L. B. Asprey by ignition of the nitrate in air. The americium stock which was used may have contained a few per­ cent lanthanum. Sample B was prepared by Eyring from a much purer americium stock by heating the oxalate in air. * Some of this material subsequently was heated in a small quarts bomb to 500° C. with oxygen at 90 atm. pressure; the product is designated as sample C. The values observed for the unit cell dimension are compared in Table 1L The results for samples B and C show that the high pressure oxidation produces no significant change in the composition of this phase. Using the purer americium stock, Asprey and Cunningham^ measured the amount of oxygen absorbed by americium (13) L. B. Asprey and B. B. Cunningham, to be published. sesquioxide when heated in oxygen. The result corresponds to AmOx for the formula of the dioxide, with x * 1.98 - 0.02, if AmgOj is the correct composition of the sesquioxide. Thus the ''black dioxide" has very nearly the ideal composition, rather than an intermediate composition like the so-called Pr^O^. The deviation of sample A from samples B and C, though small, is outside the experimental precision. The difference corresponds ***** -9 UCRL-2101 to an oxygen defect in sample A of 0. 01 O per Am, estimated from the data of McCullough** for rare earth oxide systems. This defect could (14) J. D. McCullough, J. Am. Chem. Soc. 72, 1386-1390 (1950). be the result of an impurity of about 4 atomic percent of a trivalent rare earth element (probably lanthanum) in sample A. Table II Unit Cell Dimension of Americium Dioxide Sample a (A) A 5.387 ♦ 0.001* B 5.383 t 0.001 C 5.383 to .001 Zachariasen10 5.383 t 0.005tb Zachariasen** 5. 388 t 0.003ab aPurity uncertain bCorrected from kX units. - 10- UCRL-2101 Americium Oxychloride Americium oxychloride was prepared by Dr. L. B. Aeprey by accidental contamination in an experiment designed to yield the sesquioxide by hydrogen reduction ol the dioxide. It was identified by its powder diffraction pattern which corresponded to the PbFCl type structure,15 with the tetragonal unit cell dimensions (IS) W. Nieuwenkamp and J. If. Bijvoet, Z. Krist. 81, 469-474 (1931). a - 4. 00 t 0. 01 A, c = 6. 78 t 0. 01A. A second sample was prepared by C. W. Koch by heating An^O^ at 500° C. in a mixture of HC1 and HgO vapor. The pattern again corresponded to the unit cell dimensions listed above. The atoms are located in the following special positions of space group —P4/nmm: 2 Am in (c) : 0, 1/2, u; 1/2, 0, u 2 Cl in (c) : 0.

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