THECRYSTAL STRUCTURE OF YTTRIUM NITRIDE
Sept., 1957
1237
then we can write for the thermodynamic equilibrium constant
indicate several species of intermediate widths since the width of the resonances varies gradually as the proportion of alcohol increases until no hyperfine lines are resolvable in the pure alcohol. Representative spectra are given in Fig. 2 for different prowhere X,, is the mole fraction of pyridine. The portions of alcohol. From the shape of the hyperapproximations in (15) should be good ones. The fine envelope, the individual widths of the hyperfine maximum value for X,, is 0.04 in the measurements lines can be estimated. A plot of this width us. so that the activity of pyridine should equal the mole fraction of water is given in Fig. 3. From this mole fraction and the activity of water should be we can estimate the width of an individual hyperapproximately one. Further the charge on the fine line in absolute alcohol t o be about 120 gauss complex ion and the uncomplexed ion are the same which,is consist,ent with a value for D of about 0.01 so that the ionic strength is a constant and the ratio cm. -l. of concentrations should equal the ratio of activities Other Transition Ions for the two ions. If eq. 15 is valid, then a plot of Most ions in the first transition group not yet log,, [Mr~(py).+~]/ [Mn+2]versus loglo X,, should give a straight line of slope n. Such a plot is given mentioned have rather large asymmetries in their in Fig. 1. The straight line obtained gives the spin Hamiltonian and will give lines too broad t o values of n = 1.06 and K = 130 indicating the be detected easily. Attempts t o detect the resopredominant species in these solutions is Mn- nance line in 1M solutions of X C l 2were unsuccess( p ~ ) + ~If. we assume the difference of n from ful, I n crystals containing the hydrated nickel ion unity to be significant and due to the existence of R the axial spin-spin term is rather large with D 2 This is too large ever to be averaged out second smaller complexing constant for M n ( ~ y ) ~ cm.-*. +~ we can estimate from the data values for the first so it is not difficult to understand why no resoand second complexing constants. These values nance was found. Similarily, large anisotropy in the gyromagnetic areK1 = 90 10andKz = 4 2. A similar study was made using ethyl alcohol in ratio yields resonance lines too broad for detection place of the pyridine. In this case the resonances in the case of Fe+2and Co+'.
-
*
*
THE CRYSTAL STRUCTURE OF YTTRIUM NITRIDE BY CHARLES P. KEMPTER, N. H. KRIKORIAN AND JOSEPH C. MCGUIRE Los Alamos Scienti$c Laboratory, llniversitl~of California, Los t l l a m o s , New Mexico Received May d d , lQ67
Pttrium nitride was prepared by converting yttrium met8alto YH? and then to YN. The polycrystalline YN was examined by X-ray diffraction, using both photographic and diffractometric methods. Ytt.rium nitride has space group 0.006 A. at 23' and :he calOh6-Fm3m (NaC1 structure-type) nnd 4 (YNJ per unit cell. The lattice constant is 4.877 culated density is 5.89 i 0.02 g./cm.a at 23 ; the pycnomatric density was found to be 5.60 i 0.05 gJcm.3 at 20 The melting point of YN is 22670' in the presence of one atmosphere of nitrogen.
*
Introduction Of the Group I11 transition metal nitrides, structural data have been published for ScN and LaN. Becker and Ebertl re orted a rock salt structure for ScN with a = 4.44 , and a calculated density of 4.21 g./cc. at room temperature. Iandelli and Botti2 reported an NaC1-type structure for LaN with a = 5.275 A. More recently Young and ZieglerSfound a lattice constant of 5.295 ==! 0.004 A. for LaN, and concluded that the lattice was the NaCl type. For the lattice constants reported in references 1, 2 and 3, we calculated room temperature densities of 4.47, 6.92 and 6.84 g./cm.a, respectively. Experimental
H
Yttrium sawings were obtained with a small circular saw using anhydrous ethanol as a coolant. First attempts to prepare YN by heating yttrium sawings in nitrogen yielded only 9% YN in 24 hours a t 900'; therefore, two variations (1) K. Becker and F. Ebert, Z.Physik, 81, 268 (1925). (2) A. Iandelli and E. Botti, Atti. accad. Lincei, CEassa sei. fis., mat. nat., %6, 129 (1937). (3) R. A. Young and W. T. Ziegler, J . Am. Chsm. Soc., 74, 5251 (1952).
.
of the method demihed by Eick, Baenziger and Evring' were used. The yt8triummetal chips were first converted to YH2 by reaction with hydrogen at 550' in a quartz tube. The material was then heated to 900' in the presence of a measured quantity of spectro nitrogen. At this temperature the hydride had an observed decomposition pressure of 25 mm. The gas mixture was circulated over the hydride by means of an automatic Toepler pump, and over activated uranium turnings a t 200' where the evolved hvdrogen was continuallv removed. This process was cont
