The preparation and characterization of beta-tungsten, a metastable tungsten phase
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T H E s t a b l e c r y s t a l s t r u c t u r e of t u n g s t e n ( a - W ) is body c e n t e r e d cubic. However, a m e t a s t a b l e f o r m of t u n g s t e n (/3-W) has been r e p o r t e d ~ which p o s s e s s e s the A-15 cubic c r y s t a l s t r u c t u r e containing eight a t o m s p e r unit c e l l . The l a t t i c e p a r a m e t e r o f / 3 - W is 5.036~,, and i t s c a l c u l a t e d d e n s i t y is 19.0 g p e r cu cm. B e t a - t u n g s t e n (/3-W) was f i r s t o b s e r v e d in 1931 as p a r t of the d e n d r i t i c m e t a l l i c d e p o s i t f o r m e d on the cathode a f t e r e l e c t r o l y s i s of p h o s p h a t e m e l t s below 650~ ~ T h e / 3 - W p h a s e has a l s o b e e n o b s e r v e d in v a p o r - d e p o s i t e d tungsten f i l m s . 2-4 However, the m o s t d i r e c t m e t h o d of obtaining X - r a y p u r e * / 3 - W is by h y -
d r o g e n r e d u c t i o n of WOs, 5-12 which can be c o n s i d e r e d to o c c u r in two s t e p s : 400~
' WO~.9 + 0.1 HaO 440~
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