74. Hafnium Oxide, HfO, (Monoclinic) Contributed by SEYMOUR GELLER and ERNEST CORENZWIT Bell Telephone Laboratories, Inc., Murray Hill, N. J.
N RESPOXSE
to a number of requests for a publication outlet for
I incomplete descriptions of crystallographic data, this monthly column is now being opened for the publication of such material, Two examples of partial descriptions are published this month: one, principally x-ray data and the other principally optical and morphological data. Most of the data to be published will still be in the form of complete descriptions; however, because of the usefulness of partial descriptions it is believed that through this means a great deal of worth-while data can be made available. Monoclinic hafnium oxide is not a new discovery. The compound was reported by the von Hevesy ( 1 ) in 1932. However, von Hevesy did not report the powder data nor could it be found in a rather ex%ensiveliterature survey. The hafnium oxide reported herein was made by direct combination of a very m a l l amount of high purity hafnium (supplied by the Foote Mineral Co.) with oxygen at 1100" C. in a closedend platinum-rhodium wound resistance furnace. The oxide thus formed was allowed to cool slowly (over a period of 16 hours) to room temperature. No change in phase occurred when this compound was reheated to 1400' C. in an induction furnace and quenched. The monoclinic hafnium oxide is white. As expected, it is isomorphous with ZrOz (2), the lattice constants being very close to those of the latter compound. They are: a = 5.12, b = 5.18, c = 5.25 A,, all Rrithin =k0.02 A., and p = 98 f 0.5". The space group is P21/c. With four molecules per unit cell, the calculated density is 10.3 grams per ml. The powder diffraction photographs were taken with a North
75.
Table I. X-Ray Powder Diffraction Data for Monoclinic Hafnium Oxide d , A.
Obsd. 5.07 3.68 3.61 3.15 2.82 2.59 2.52 2.48 2.32 2,196 2.171 2.006 1.981 1.838 1.807 1.794 1.768 1.684 1.653 1.634 1.600 1.580
Calcd. 5 08 3.68 3.62 3.14 2.82
{f;;
2.53 2.47 2.33 j2.32 2.30 2.20
{i:;: 2.01 {;:;; {;
1.81 1.79 1.77
{:::
1.65
[i!;
;:1
I/Il
2 4 3
lo+ 10 6 5 2
hkl 100 011
119 111 111
102 012
5 6
211
3 3 4
112 211
6 6 2
3 5 6
229 12_2 221
221 013
d, A., Obsd. 1.501 1.486 1.467 1.439 1.410 1.352 1.318 1.299 1.295 1.263 1.256 1.237 1.203 1.172 1.160 1.153 1.143 1.134 1.121 1,108 1.099 1.084 1.070 1.049 1.039 1.025
I/II 4 4 5 3 5 2 4 1 3
