X-ray evidence for CrBO₃, VBO₃, and TiBO₃ with calcite structure

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Reference

X-ray evidence for CrBO ₃ , VBO ₃ , and TiBO ₃ with calcite structure

SCHMID, Hans

Abstract

The borates were prepd. by heating the metal oxides, halides, and H3BO3 in a sealed quartz tube. Structures were deduced from x-ray powder diagrams.

SCHMID, Hans. X-ray evidence for CrBO

, VBO

, and TiBO

with calcite structure. Acta Crystallographica , 1964, vol. 17, no. 8, p. 1080-1081

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1 / 1

Reprinted f r o m Acta Crystallographica, V o l . 17, P a r t 8, August 1964

P B I N T E D I N D E N M A K K

Acta Cryst. (1964). 17, 1080

X - r a y evidence for CrBOg, V B O 3 and T i B O g w i t h calcite structure.

{Received 31 March 1964) I n t h e course of p r e p a r a t i o n s of boracites b y gas phase

t r a n s p o r t reactions i n sealed q u a r t z tubes ( S c h m i d , 1964) we also o b t a i n e d several k n o w n a n d some n e w t r a n s i t i o n m e t a l borates via t h e gas phase.

H e r o w e w a n t t o r e p o r t o n a n e w c h r o m i u m , v a n a d i u m , and t i t a n i u m b o r a t e . T h e e x p e r i m e n t a l c o n d i t i o n s i n - d i c a t e d i n t h e f o U o w i n g are n o t o p t i m a l f o r b o r a t e f o r m a t i o n since t h e y w e r e chosen w i t h a v i e w t o o b - t a i n i n g boracites. Nonetheless t h e y m a y serve as a g u i d e :

T h e c h r o m i u m b o r a t e was o b t a i n e d as f o l l o w s : i n a sealed q u a r t z t u b e ( v o l u m e 0-08 1) t h r e e q u a r t z cruoibles c o n t a i n i n g 0-76 g BgOg, 0-3 g ( C r j O g + C r ) a n d 0-67 g C r C l j r e s p e c t i v e l y , were a r r a n g e d , one above t h e o t h e r , a n d 175 m g H j O i n t h e f o r m of H 3 B O 3 was placed i n

t h e c r u c i b l e c o n t a i n i n g C r j O g + C r . T h e sealed t u b e was h e a t e d i n a v e r t i c a l t u b u l a r f u r n a c e f o r f o u r days i n a s m a l l t e m p e r a t u r e g r a d i e n t ( r i~ 9 9 0 °C, ^ 2^ 1 0 0 0 °C) i n such a w a y t h a t t h e colder e n d of t h e t u b e was o n t o p . T h e c o o l i n g t o r o o m t e m p e r a t u r e t o o k 3 h o u r s . I n t h e c r u c i b l e , c o n t a i n i n g B j O g , C r - C l - b o r a o i t e h a d f o r m e d , a n d o n t h e w a l l s of t h e t u b e (coldest zone), hexagonal, grass-green platelets ( a b o u t 0-05 m m t h i c k a n d 0-5 m m i n d i a m e t e r ) were d e t e c t e d . T h e crystals c o u l d easily be d e t a c h e d b y d i s s o l v i n g t h e B 2 O 3 f i h n o n t h e t u b e w a l l i n b o i l i n g w a t e r .

T h e V a n a d i u m b o r a t e was f o r m e d as f o l l o w s : three q u a r t z crucibles c o n t a i n i n g 2-8 g B2O3, 1-34 g ( V 2 O 5 + 3 V ) a n d 2-54 g V C I 2 r e s p e c t i v e l y , were p l a c e d i n a q u a r t z

1 0 8 1 S H O R T C O M M U N I C A T I O N S

T a b l e 1 . Observed and calculated lattice spacings and visually estimated intensities for T i B O j , V B O 3 , C r B O j Indices refer to the t r i p l y p r i m i t i v e hexagonal cell.

(The lattice spacings should be compared w i t h those found b y Bernal, Struck & W h i t e for Feo.gGao.iBÖg: a n = 4-631 + 0-005, C H = 14-42 ± 0-01, aR = 5-496 Ä ; « = 49° 38')

T i B O , VBO3 C r B O ,

hkl do de lo do de io do de lo

102 3-548 3-554 45 3-449 3-465 50 3-438 3-462 55

104 2-737 2-740 100 2-641 2-655 100 2-631 2-648 100

110 2-336 2-335 30 2-284 2-286 25 2-277 2-286 18

113 2-113 2-113 60 2-056 2-062 50 2-049 2-061 45

202 1-950 1-9.50 42 1-905 1-909 35 1-896 1-908 20

204 1-774 1-777 25 1-732 1-733 32 1-724 1-731 18

116

108

1

1-692 1-650

1-631 1-650

1-630 50

40 1-644

1-621 1-648

1-624 50

212 1-480 1-497 5 1-464 1-465 25 1-465 1-465 40 20

214 1-415 1-414 10 1-380 1-381 30 1-380 1-380 28

1,0,10 _{208 1-370}

—

—

1

300 10

119

j

j

1

0,0,12 1-242 1-242 30 1-194 1-193 60 1-187 1-187 60 10

2,0,10 1-200 1-200 10 1-162 1-160 20 1157 1-156 25

218 1-181 1-181 40

aji = 4 - 6 7 0 ± 0 - 0 0 8 A « H = 4-573 + 0-005 A a n = 4-573 ± 0 - 0 0 5 Ä C H = 14-90 ± 0 - 0 5 Ä C H = 14-32 ± 0 - 0 1 A C H = 14-23 ± 0 - 0 1 A O R = 5-65 A « E , = 5-453 A O R = 5-434 Ä

a = 48° 48' « = 49° 24' « = 49° 46'

t u b e (as above). T h e HaO-dosis w a s 4 5 m g . T h e sealed t u b e w a s heated f o r 1 2 hours i n a s m a l l g r a d i e n t ( 5 ° p e r 2 0 c m ) a t a b o u t 9 0 0 "C, t h e colder e n d b e i n g o n t o p . Cooling t o o k 2 hours. I n t h e qu.artz c r u c i b l e , o r i g i n a l l y c o n t a i n i n g B2O3, h e x a g o n a l r e d bro-vm ( i n t r a n s m i t t e d l i g h t ) platelets (dimensions l i k e those of t h e c h r o m i u m borate) h a d f o r m e d . N o b o r a c i t e w a s o b t a i n e d , b u t s m a l l V2O3 crystals h a d f o r m e d o n t h e w a l l s o f t h e t u b e .

T h e t i t a n i u m borate w a s o b t a i n e d as f o l l o w s : t h e three q u a r t z crucibles (as above) c o n t a i n e d 2 - 8 g BgOg, T 3 g T i O a n d 6 - 0 g T i l j respectively. T h e w a t e r dosis w a s 1 7 5 m g . T h e w h o l e t u b e w a s m a i n t a i n e d i s o t h e r m a l f o r 4 8 h o u r s a t 9 0 0 °C. Cooling t o o k 3 h o u r s . I n t h e c r u c i b l e , c o n t a i n i n g B2O3, h e x a g o n a l platelets, r e d b r o w n i n t r a n s m i t t e d l i g h t a n d greenish d a r k b r o w n as a b u l k i n reflected l i g h t , h a d f o r m e d . T h e c r y s t a l dimensions were like those of t h e c h r o m i u m c o m p o u n d .

C h r o m i u m Kx p o w d e r d i a g r a m s of a l l n e w phases a n d Cu /-Ca-Weissenberg p h o t o g r a p h s of t h e c h r o m i m n c o m - p o u n d were m a d e . W e c o u l d show t h a t a l l three c o m - potinds are i s o s t r u c t u r a l a n d belong t o t h e calcite t y p e , as do t h e reoently discovered i r o n borates w i t h t h e goneral f o r m u l a Fei^:j:M:jB03 ( B e r n a l , S t r u c k & W h i t e , 1 9 6 3 ) .

A l t h o u g h there w a s n o t s u f f i c i e n t substance f o r che- m i c a l analysis, t h e calculated a n d observed d-values a n d t h e v i s u a l l y e s t i m a t e d intensities (Table 1 ) , c o m p a r e d w i t h those of t h e i r o n b o r a t e , leave n o d o u b t t h a t w e

h a d t o d o w i t h t h e borates C r B O j , V B O 3 a n d T i B 0 3 . T h e meohanisms of t h e t r a n s p o r t o f t h e oxides are n o t y e t clear; p r o b a b l y halides a n d o x y h a l i d e s (c/. Schäfer, 1 9 6 2 ) of h i g h e r m e t a l v a l e n c y t h a n t w o , f o r m e d b y d i s p r o p o r t i o n a t i o n of t h e halides M X g , were i n v o l v e d . A s t o f u r t h e r e x p e r i m e n t a l d e t a i l s a n d a discussion of t h e B2O3 t r a n s p o r t , t h e c i t e d paper o n boracites s h o u l d be referred t o .

T h e synthesis p r i n c i p l e is q u i t e generally applicable t o borates, p r o v i d e d t h a t a suitable t r a n s p o r t r e a c t i o n of t h e i n v o l v e d m e t a l oxide c a n be f o u n d . A n e l a b o r a t i o n of t h e m e t h o d seems therefore v e r y p r o m i s i n g f o r o b - t a i n i n g b o t h Single crystals a n d y e t u n k n o w n c o m p o u n d s , e.g. A I B O 3 , G a B O s , etc.

T h e a u t h o r wLshes t o t h a n k G . K l i e g l f o r t h e ohemical p r e p a r a t i o n s .

R e f e r e n c e s

B E R N A L , I . , S T R U C K , C . W . & W H I T E , J . G . ( 1 9 6 3 ) .

Acta Cryst. 16, 8 4 9 .

S C H Ä F E R , H . ( 1 9 6 2 ) . Chemische Transportreaktionen.

W e i n h e i m .

S C H M I D , H . ( 1 9 6 4 ) . J . Phys. Chem. Solids. T o be p u b - iished.

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