Neutron diffraction investigation of ordered structures in the titanium-oxygen system
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s o m e t i m e it had b e e n thought that the T i - O s y s t e m c o n s i s t e d of a wide r a n g e of i n t e r s t i t i a l solid s o l u tions b a s e d on the l o w - t e m p e r a t u r e ot m o d i f i c a t i o n of t i t a n i u m . 1 The s o l u b i l i t y of oxygen in ot-Ti has b e e n a s s u m e d to be 32 at. pet. R e c e n t s t u d i e s showed, howe v e r , that in this c o n c e n t r a t i o n r e g i o n t h e r e is no g r a d ual change in such p r o p e r t i e s as e l e c t r i c a l r e s i s t a n c e , t h e r m a l e l e c t r o m o t i v e f o r c e , m i c r o h a r d n e s s , and the r a t e of o x i d a t i o n f -5 A c c o r d i n g to the data of i n v e s t i g a tion, ~ on the c u r v e s for the c o m p o s i t i o n a l d e p e n d e n c e of the a b o v e - m e n t i o n e d p r o p e r t i e s for alloys a n n e a l e d for a p r o l o n g e d p e r i o d of t i m e , t h e r e can be o b s e r v e d two s i n g u l a r points for which the c o n c e n t r a t i o n s of oxygen a r e 14.3 and 25 at. pct, r e s p e c t i v e l y . These s i n g u l a r points c o r r e s p o n d to the c o m p o s i t i o n s of the s u b o x i d e s Ti60 and Ti30. X - r a y s t r u c t u r a l a n a l y s i s of p o l y c r y s t a l l i n e s a m p l e s showed 6'7 that when the c o m p o s i t i o n of the suboxide c o r r e s p o n d s to Ti20 an o r d e r e d s t r u c t u r e a p p e a r s . The o r d e r e d s t r u c t u r e for c o m p o s i t i o n TiaO was detected by H o l m b e r g 8 and c o n f i r m e d b y D u b e r t r e t and Lehr u s i n g the X - r a y s t r u c t u r e a n a l y s i s method. 9 But this method f a i l e d to r e v e a l the o r d e r e d s p a c i n g of oxygen a t o m s in the case of the suboxide TiaO. In 1966 an e l e c t r o n d i f f r a c t i o n study was p u b l i s h e d of the o r d e r ing p r o c e s s in a single c r y s t a l l i n e s a m p l e of TieO. 19 Thus it was of i n t e r e s t to m a k e a n e u t r o n d i f f r a c t i o n study of the o r d e r i n g of oxygen a t o m s in Ti~ a l l o y s . The n e u t r o n d i f f r a c t i o n method is the m o s t p r o m i s i n g for the study of the s p a c i n g of the light a t o m s in the m e t a l l a t t i c e owing to the fact that the a m p l i t u d e s of c o h e r e n t n e u t r o n s c a t t e r i n g of t i t a n i u m and oxygen a t o m s a r e c o m p a r a b l e , i.e., 0.38 and 0.58 • 10 -1~ c m , respectively. The a l l o y s were p r e p a r e d by a method which has b e e n p r e v i o u s l y d e s c r i b e d , z In Table I a r e given the c o m p o s i t i o n s of the alloys and t h e i r c h e m i c a l a n a l y s e s . The a n a l y s i s of oxygen in the s a m p l e s was c a r r i e d out by the m e t h o d of c o m b u s t i o n in oxygen. The c o m p o s i tion of the a l l o y s was also checked by m e a s u r i n g the p a r a m e t e r s of the unit cell on a flat s a m p l e with the aid of X - r a y a p p a r a t u s URS-501 and by c o m
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