Conductivity of Nasicon ceramic membranes in aqueous solutions

Solid State lonics5 (1981) 315 316 North-HollandPublishingCompany

CONDUCTIVITY

OF N A S I C O N

CERAMIC

J. J. A u b o r n

Murray

and

HEMBRANE.~

D. W.

IN A Q U E O U S

Johnson,

Bell L a b o r a t o r i e s Hill, N e w J e r s e v

SOLUTIONS

Jr.

07974

The c o n d u c t i v i t y of N A S I C O N (Na3Zr2Si2POl2) c e r a m i c m e m b r a n e s was m e a s u r e d b e t w e e n nickel e l e c t r o d e s in a a u e o u s s o d i u m n i t r a t e s o l u t i o n s . E x p e r i m e n t s w e r e c o n d u c t e d o v e r the t e m p e r a t u r e r a n g e 0-100°C. The data are in mood a g r e e m e n t w i t h e x t r a p o l a t i o n of p r e v i o u s l y p u b l i s h e d and dc c o n d u c t i v i t y data taken at h i g h e r t e m p e r a t u r e s .

N A S I C O N (Na3Zr2Si2POl2) c e r a m i c is a fast s o d i u m ion c o n d u c t o r at high temperature. Its c o n d u c t i v i t y at 300°C is c o m p a r a b l e to that of s o d i u m 8-alumina.l, 2 In c o n t r a s t to S-alumina, it is not s e n s i t i v e to d e g r a d a t i o n by moisture. Its c o n d u c t i v i t y at r o o m t e m p e r a t u r e is s i m i l a r to t h o s e of s o d i u m salts in n o n - a q u e o u s solution, m a k i n g it A p p r o p r i a t e for low t e m p e r a ture s o d i u m cells. 3 W e n o w find that the c o n d u c t i v i t y of N A S I C O N in a q u e o u s s o d i u m n i t r a t e s o l u t i o n b e t w e e n 0 and 1 0 0 ° C is c l o s e to that e x p e c t e d from e x t r a p o l a t i o n of d a t a t a k e n for s o d i u m ion c o n d u c t i o n at h i q h e r t e m p e r a t u r e . 4 C e r a m i c m e m b r a n e s w e r e p r e p a r e d as follows. Na3Zr2Si2POl2 powder was made by c a l c i n i n g a m i x t u r e of N a 3 P O 4 - 1 2 H20, ZrO 2 and SiO 2 at I 1 3 0 ° C for 4 hours. This m a t e r i a l w a s m i l l e d u n d e r a c e t o n e for 30 h o u r s u s i n g ZrO 2 balls, dried, a n d i s o s t a t i c a l l y p r e s s e d into c y l i n d r i c a l b a r s a p p r o x i m a t e l y 2.5 cm in d i a m e t e r . Sample discs were diamond m a c h i n e d from the s i n t e r e d bars. The c o n d u c t i v i t y w a s m e a s u r e d in a P y r e x cell w i t h two 1.2 cm d i a m e t e r n i c k e l disc e l e c t r o d e s 0.6 cm a p a r t s e p a r a t e d by a 1.9 cm d i a m e t e r by 0.05 cm thick N A S I C O N m e m b r a n e sealed to the g l a s s w i t h K o v a r s e a l i n g glass. The two cell c o m p a r t m e n t s w e r e f i l l e d w i t h a q u e o u s 1 M N a N O 3 solution, and the a s s e m b l y p l a c e d in a c o n t r o l l e d t e m p e r a t u r e chamber. Data w e r e t a k e n f r o m 0 to 1 0 0 ° C in 20°C i n c r e m e n t s . R e s i s t a n c e m e a s u r e m e n t s were taken on a G e n e r a l Radio 1 6 5 0 B I m p e d a n c e B r i d g e c o m p e n s a t e d for c a p a c i t i v e r e a c t a n c e w i t h an e x t e r n a l d e c a d e capacitor. An e x t e r n a l 5 mV, 20 kHz s o u r c e was used w i t h an o s c i l l o s c o p e detector. Measured resistances were corrected for the r e s i s t a n c e of the 1 M NaNO~ solution and conductivities calcul~ted

0 167-2738/81/0000

u s i n g the g e o m e t r i c membrane.

dimensions

of

the

The 0 to 100°C c o n d u c t a n c e d a t a are p r e s e n t e d in Fig. 1 as an A r r h e n i u s plot. A least s q u a r e s fit y i e l d s a pree x p o n e n t i a l t e r m of 68000 o h m - l c m - l d e g and an a c t i v a t i o n e n e r g y of 7.62 k c a l / m o l e (0.330 eV). This s i n g l e p r o c e s s is c o m p a r a b l e to e x t r a p o l a t i o n of s o d i u m ion c o n d u c t i v i t y in N A S I C O N b e l o w 1 5 0 ° C m e a s u r e d by o t h e r s 4 and is not a f f e c t e d by the a q u e o u s solvent.

TEMPERATURE (deg C) |

i

'

i

'

,

',

,

i

,

" l

T

/|

~7

I

&9

I

Z9

I

&6

|

|

I

&l

&2

K3

.,

I~/T

!

~4

I

K5

I

~6

(l/degK)

F i g u r e i: A r r h e n i u s plot of c o n d u c tivity~NASICON m e m b r a n e in a q u e o u s s o d i u m n i t r a t e solution. I. H. Y-P. Hong, Mat. Res. Bull. i~, 173 (1976). 2. J. B. G o o d e n o u ~ h , ~{. Y-P. IIong and J. A. Kafalas, Mat. Res. Bull. i~, 203 (1976). 3. J. J. A u b o r n and S. M. G r a n s t a f f , Jr., Proc. 15th IECEC, 575 (1980). 4. A. Hooper, J. E l e c t r o a n a l . Chem. 109, 161 (1980).

0000/$02.75 © North-Holland Publishing Company