Inorganic Chemistry COVTRIRUTIOV FROTI
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RESEARCH LABOR4TORY, WASHINGTON D C 20390
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The Hydrothermal Preparation, Single-Crystal Lattice Parameters, and Decomposition Data for Some Lanthanide Dihydroxy Chlorides and the Related Hydroxy Chloride, Yb30(OH)&12 BY FORREST L. CARTER
AND
SOLOMON LEI'I?\TSON
Recei.Lled Muuch 17, 1969 T h e dihydroxy chlorides of La, Kd, Sm, Gd, and Y and the related compound Yb80(0H):Cl2 have been prepared hydrothermally a t 500". The compounds La(0H)BCl. ?id(OH)eCl, Sm(OH)eC1, and Gd(OH),CI form an isomorphous series whose monoclinic lattice parameters have been determined by single-crystal techniques and fitted to quadratic equations by the method of least squares. Accurate lattice parameters for the orthorhombic form of U( OH)SCl, prepared previously, and the orthorhombic UbaO( OH)jCl? also have been determined. T h e monoclinic rare earth dihydroxy chlorides decompose thermally under nitrogen to form the oxychlorides and water. Approximate heats of decomposition have been determined. Yb30( OH)jC12decomposed to the sesquioxide and Y(0H)nCl to a mixture of the oxychloride and sesquioxide.
Introduction In the course of preparing yttrium-iron garnet single crystals under varying hydrothermal conditions two different crystalline forms of yttrium dihydroxy chloride, Y (OH)gCl, and a related hydroxy chloride Y30(OH)6C1zhave been isolated by Klevtsov, Klevtsova, and their cou~orkers.~-~ In an attempted hydrothermal preparation of lanthanum aluminate a t 500" from LanOs and AlCl3.6HZOin a 15% NH4C1 solution S. L. obtained the first known crystalline rare earth dihydroxy chloride, La(OH)zC15 (in addition to o(-X1203). In view of considerable current interest in the electromagnetic properties of single crystals containing the rare earth elements, it appeared desirable to characterize some of the rare earth analogs of the yttrium hydroxy chlorides. Data on the preparation, lattice parameters, and thermal decomposition of the monoclinic crystals of La(OH)zC1, I\Jd(OH)zCl,Sm(OH)2C1, and Gd(OH)&l are given here in addition to similar information for the orthorhombic form of Y(OH)zCl and for YbaO(OH)5C12. An additional, and, in the long range, more compelling reason for the study of these materials is that such isomorphous series of rare earth compounds represent ideal grounds for testing theories of transition metal covalent bond formation (among other theories) as a function of d character and size. Structural determinati0ns2-*>~have shown that the four compounds Y(OH)&l (orthorhombic), Y (OH)2C1 (monoclinic), Ye0 (OH)5C12,and La(0H)ZCl are closely related' layer (1) P. 1 7 . Klevtsov, R . F. Klevtsova, and L. P. Sheina, Zh. Stvukl. Khim., 6, 469 (1965). (2) R . F. Klevtsova and P. V. Klevtsov, Dokl. A k a d . N a u k S S S R , 162, 1049 (1965). ( 3 ) R. F. Klevtsova and P. V. Klevtsov, Zh. Slruki. K h i m . , 7, 566 (1966). (4) R. F. Klevtsova, L. P. Kozeeva, and P. V. Klevtsov, I r v . A k n d . Xnuk S S S R , Neovgax. Matei.iaZy, 3, 1430 (1967). (5) N. V. Aksel'rud and V. B. Spivakovskii (Zh. .Veorgan. Khinz, 5 , 327, (1960)) have described the formation of presumably amorphouv Ld(oH)zCI by the addition of NaOH solution to one containing LaCls. They established the composition of the precipitate by a potentiometric method. ( 6 ) See a preliminary account of the structure by F. L. Carter, Proceedings of the Sixth Rare Earth Conference, M a y 3-5, 1967, Gatlinburg, Tenn., 1967, p 187. The completed structure will be submitted for publication in the near future. (7) K. Dornberger-Schiff and R. F. Klevtsova, Acta Cryst., 22, 436 (1967).
type of structures where the layers are held together by predominantly 0-H. C1 hydrogen bonds. This suggests that a short bond distance obtained in such materials is likely to be a more valuable representation of an unstrained bond than in a simpler compound like LaOCl with three-dimensional arrays of strong bonds. While the structures of the yttrium compounds have all been reported as being centrosymmetri~,~-~ the lanthanum dihydroxy chloride is noncentrosymmetric. This suggests that these lanthanide compounds are not only suitable candidates for ferroelectric, magnetoelectric, and other similar studies, but also, in consideration of their layer structure, candidates for the testing of theories of magnetic cluster formation. '
Experimental Section Materials.-Reagent grade ATHdCl, A'11c13.6Hn0, H S 0 3 , and HC1 were used. The rare earth oxides, all 99.9% pure with respect to the lanthanides, were from American Potash (LapOa, Smz03, Gd203, and \'nos), Research Chemicals (xd203), and Michigan Chemical (Ubz03). Hydrothermal Preparations.-The vessels used in the preparations listed in Table I were of two types. One described by May, et ~ l . consisting , ~ of a platinum liner in a nichrome carrier, was found to be operable a t 20,000 psi and ;i5Oo. The second type was similar to that described by Tuttle and Friedmang but with a gold liner and a single ?-in. KO. 12 thread. After loading and closure, the vessel was heated in a cylindrical furnace a t 3" and maintained for 2-5 days a t temperature. 500 =I= X-Ray Data.-The new single-crystal lattice parameter data presznted in Table I1 were manually collected on a carefully aligned Picker Nuclear four-circle goniostat using Mo K a radiation (Aal 0.70926 A). All crystalline specimens used had a maximum dimension no larger than 110 fi and were mounted on specially stable arcless goniometer heads.I0 The crystals were visually perfect and gave sharp (el;ception-Y(OH)2Cl), smooth peaks at high 78 (narrow slit width, slow scan). The 20 peak positions were determined using quarter-peak intensity heights (half for U(OH)2C1) of the Kal line. For each specimen x , p, w , and 29 ( > 6 a o ) were measured to a precision of 0.01' for more than 30 reflections. The errors listed in Table I1 are estimated from a comparison of lattice parameters for different crystals of the same composition and probably include the effects ( 8 ) I. May, J. J. Kowe, and R . Letner, U. S. Geological Survey Profes. sional Paper 625-B, Geological Survey Research, 1965, p 165. (9) 0. F. Tuttle and I. I. Friedman, J . A m . Chem. Soc., 7 0 , 919 (1948). (10) F. L. Carter and W.C. Sadler, J . A p p l . Cryst., 2 , 145 (1969).
LANTHANIDE DIHYDROXY CHLORIDES2789
Vol. 8, No. 12, December 1969 TABLE I HYDROTHERMAL PREPARATION OF DIHYDROXY CHLORIDES AT 500 f 3'" Final pH
Run
Reagents
1
LazOa AICls.6HzO 15% NHdC1 soln LazOa 1 N HCl soln 15% NHaCl s o h LazOa 1 N HC1 s o h LazOs 15% Nd?Os 15% N H C 1
0,001 mol
