VANADATE SEMICONDUCTING GLASSES DOPED WITH OXIDES OF OTHER TRANSITION METALS

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VANADATE SEMICONDUCTING GLASSES DOPED WITH OXIDES OF OTHER TRANSITION METALS

L. Bogomolova, V. Jachkin, M. Glassova, S. Spasibkina

To cite this version:

L. Bogomolova, V. Jachkin, M. Glassova, S. Spasibkina. VANADATE SEMICONDUCTING

GLASSES DOPED WITH OXIDES OF OTHER TRANSITION METALS. Journal de Physique

Colloques, 1981, 42 (C4), pp.C4-993-C4-996. �10.1051/jphyscol:19814216�. �jpa-00220845�

VANADATE SEMICONDUCTING GLASSES D O P E D W I T H O X I D E S OF OTHER TRANSITION METALS

L.D. Bogomolova, V.A. Jachkin, M.P. Glassova and S.N. Spasibkina

J n s t i t u t e oJ Nuclear Phgsics, Moscou S t a t e U n i v e r s i t y , Moscou 117234, USSR

A b s t r a c t . - The EPR s p e c t r a , e l e c t r i c a l c o n d u c t i v i t y and a c t i v a t i o n e n e r g y have been measured i n barium-vanadate g l a s s e s doped w i t h CuO, Mn203, F e 2 0 3 , Co2G3 and Cr203 i m p u r i t i e s i n c o n c e n t r a t i o n

from 0 . 1 t o 7 w t . % . The r e s u l t s a r e i n t e r p r e t e d i n t e r m s o f d i s t i n c t i n t e r a c t i o n s between vanadium and i m p u r i t y i o n s .

I n t r o d u c t i o n . - The EPR s t u d y o f barium-vanadate g l a s s e s w i t h CuO i m - p u r i t y h a s shown ( l ) t h a t c u 2 + and

v4+

i o n s form t h e mixed exchange

p a i r s . The s i n g l e EPR l i n e w i t h g = 2 . 0 8 h a s been a t t r i b u t e d t o t h e - ae p a i r s c o u p l e d by s t r o n g f e r r o n a g n e t i c i n t e r a c t i o n . The f o r m a t i o n o f mixed p a i r s l e a d s t o t h e i n c r e a s e i n t o t a l c a r r i e r c o n c e n t r a t i o n by t h e i n p u r i t y e l e c t r o n s b e l o n g i n g t o t h e p a i r s and t o t h e change

i n t h e a c t i v a t i o n e n e r g y and e f f e c t i v e m o b i l i t y .

The aim of t h e p r e s e n t work i s t h e s t u d y o f t h e v a l e n c e s t a t e s o f t h e i n p u r i t y t r a n s i t i o n m e t a l s (Mn,Fe,Co,Cr) i n barium-vanadate g l a s s e s , t h e i r i n t e r a c t i o n s w i t h vtinadium i o n s and e f f e c t s on t h e e l e c t r i c a l c o n d u c t i v i t y o f t h e s e g l a s s e s .

Experimental.- The g l a s s e s w i t h t h e b a s e c o m p o s i t i o n 35 mol.% BaO and 6 5 mo1.8 V 0 ( d e n o t e d by Bv) were p r e p a r e d . Four s e r i e s o f

2 5

g l a s s e s BV doped w i t h d i f f e r e n t i m p u r i t i e s o f t r a n s i t i o n m e t a l oxid- e s (11 0 ) were i n v e s t i g a t e d . These were g l a s s e s BV c o n t a i n e d from

2

3

0.1 t o 5 wt."/on 0 ( S e r i e s fln-BV), g l a s s e s BV c o n t a i n e d from 0.3 t o 2

3

7 w t . % Fe 0 ( S e r i e s Fe-BV), g l a s s e s BV c o n t a i n e d f r o n 0.5 t o 7 w t . % 2 3

Go 0 ( S e r i e s CO-i3V) and g l a s s e s BV c o n t a i n e d from l t o

5

wt.,% C r 0 2 3 (S:r?es Cr-3V). EPR measurements were c a r r i e d o u t u s i n g X-band s p e c t r o m e t e r RE-l306 from 7 7 t o 470 K. The r e s i s t i v i t y was measured o v e r a t e m p e r a t u r e r a n g e f r o n 6 0 C t o a t e m p e r a t u r e n e a r t o t h e g l a s s t r a n s i t i o n ( ~ 2 6 0 - 2 ? 0 C ) u s i n g a MOM-3 ohmeter.

R e s u l t s . - We show t h e EPR s p e c t r u m o f t h e b a s e g l a s s BV i n F i g - l a . T h i s i s due t o v 4 + i o n s and c a n be d e s c r i b e d by an a x i a l s p i n S a m i l t o - n i a n w i t h p a r a m e t e r s g , , = 1.924 7 0.004,

a =

1.960

;

0.005, A , , =

= ( l 5 7 7 ~ ) . I o - ~ cm-' and A A = ( 5 4

7

2 ) . 1 0 - ~ cm -1

.

Pig.2 s h o x s t h e p a r a l l e l h y p e r f i n e s t r u c t u r e ( h f s ) components o f

v4+

EPR s p e c t r u m f o r m=7/2 and m=5/2 i n t h e g l a s s BV and i n t h e g l a s s e s o f Nn-3V s e r i e s c o n t a i n i n g 0.3 and 0 . 5 w t . % Mn203.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19814216

C4-994 JOURNAL DE PHYSIQUE

Fig.2 : Fragments of h f s s p e c t r a of a)BV- g l a s s , b ) g l a s s BV

+

+0.3 wt.% Mn203 and c ) g l a s s BV+0.5% Mn 0

2 3

EPR s p e c t r a of a ) g l a s s BV, b ) g l a s s w A o l . % Mn203, c ) g l a s s BV

+

5 wt.?; Fe 0 2 3 ( a t 300 K ) and d ) g l a s s BV +

7

w t . % Co2o3 ( a t

77 K)

It i s s e e n t h a t t h e l i n e w i d t h s of t h e h f s components a r e g r e a t e r i n t h e Mn-BV g l a s s e s t h a n i n t h e BV g l a s s , and t h e y i n c r e a s e w i t h i n c - r e a s i n g Mn203 c o n t e n t . The h f s components a r e l e s s c l e a r l y observed i n t h e samples w i t h 1 o r 2 w t . " - / 0 2 0 3 and a f t e r 2 wt.% Mn203 hyperf- i n e s t r u c t u r e of V4+ d i s a p p e a r s compietely. S i n g l e broad s y & e t r i c l i n e i s observed i n g l a s s e s c o n t a i n i n g from 3 t o 5 wt.%Mn203(Fig.lb).

The l i n e w i d t h i s almost c o n s t a n t i n t h e s e samples @ 4 3 0 Oe) and g-value v a r i e s from 2.009 t o 2.018. The i n c r e a s e i n t h e i n t e g r a t e d i n t e n s i t y of t h i s l i n e i s p r o p o r t i o n a l t o Mn 0 c o n t e n t . The width of t h e l i n e i n t h e sample c o n t a i n i n g

5

wt.% 3 M n 2 ~ 3 d e c r e a s e s from 470 t o 390 Oe when temperature i n c r e a s e s from -150 t o +200 C. No o t h e r l i n e s were observed i n t h e g l a s s e s of Mn-BV s e r i e s .

I n c o n t r a s t t o t h e Mn-BV s e r i e s t h e g=4.3 l i n e due t o i o n s i s observed i n a l l t h e g l a s s e s of Fe-BV s e r i e s . T h i s i s asymmetric w i t h peak-to-peak width about 150-160 Oe a t 0.5-1 wt.% Fe2O3. This l i n e was a l s o observed i n t h e samples w i t h h i g h Fe203 contents but i t s i n t e n s i t y and width cannot be measured because of an o v e r l a p w i t h o t h e r l i n e ( ~ i g . 1 ~ ) . I n t h e g l a @ e s c o n t a i n i n g from 0.3 t o 1 w t . % Fe 0 t h e h f s EPR spectrum of V'' i o n s i s observed c l e a r l y . The wid-

2 3

i l ' j 5.5 ^: t e n p e ~ a t u r c d e ; > ? ~ d c n c e o f t h e i n t e : : r a t e d i n t e n s i t y o f E22 s s e c t r n

60 C on K2Gq con- t e n t , wilere Pi i s a ) Yn, 5 ) P e , c ) Co.

t n s o f hfr:. c o a p o n c n t s i n c ~ e a s ? w i t h i n c r c a a i n g Pe,O, c o n t e n t , and

c. /'

t h e broad s i n g l e l i n e ,..;it'?. g s 2 i s o b s e r v e d a f t e r 2 w t . % l e 2 0 q . These r c q u l t s Ere s i ~ i l a r t o t n o c e f o r En-3V z l a s s e s . Xowever, t h e w i d t h c f t n e

$2

l i n e i s g r e a t e r i n Fe-dV g l a s c c c t h a n i n Kn-BV g l a s s e s (Yig.1) and t h i s i n c r e a s e s w i t h >'e20 c o n c e n t r a t i o n .

3

G.+ .

The :?fc ETR spectru!n ciue t o V l o n c i s o n l y o b s e r v e d i n t h e

~ l n s r e s o f t h e Co-SV s e r i e s a t r o o n t e a p e r a t u r e . The t e m p e r a t u r e dependence o r t ! ~ i n t e n s i t y c f t h j s Zi;R s p e c t r u m i n t h e g l a s s c o n t a i n i n g

7

wt.;; CO C i s shown i n 555.3. New ve:-y b r o a d l i n e app-

2 5

e a r s i n e low m a g n e t i c f i e l d a t

77 K

i n a l l t h c s a m p l e s o f s e r i e s CO-3v ( P i g . 'i )

.

m. ~ n e h f s

E?R

sspectrum due t o i s o b s e r v e d i n t h e g l a s s e s of t h c Cr-BV c e r i e s i n t h c f e n p e r a t u n e r a n g e from

77

t o 309

K.

The wi- d t h s o f h f c c o ~ g o o e n t s a r e c o n s t a n t f o r

Cr,O

c o n t e n t r a n g i n g from l t o j v t ;h. However, t h e w i d t h s o f h f s c 3components and i n t e g r - a t e d i n t e n c i t y o f t h e s p e z t r u m i n c r e a s e s s u d d e n l y when tern c r a t u r e i n c r e a s e s t o

55

C i n a l l t h e samples o f t h i s s e r i e s

(Fig.37.

Thc dependence o f t h e r e s i s t i v i t y a t 60 C on M20 c o n c e n t r a t i - on i n barium v a n a d a t c g l a s s c s i s shown i n Pig.4. I t c a n be s e e n t h a t

3

t h i s i n c r e a s e s w i t h i n c r e a s i n g

K

0 c o n t e n t i n a l l t h e s e r i e s . I n 2 3

t h e b i z a r y g l a s s 3 V t h e r e s i s t i v i t y a t 60 C i s 6.10~ ohm cm. The t e - m p o r a t u r e dependence o f t h e r e s i s t i v i t y f o r t h i s g l a s s c a n be r e p r e - s e n t e d by two s t r a i g h t l i n c a w i t h d i f f e r i n g s l o p e s , t h a t i s , w i t h two d i f f e r e n t a c t i v a t i o n e n e r g i e s . Tile a c t i v e t i o n e n e r g y Ea= 0.382 eV f r o n 60 t o 200 C and

E , e

0.15 eV a t h i g h e r t e m p e r a t u r e . T h i s r e - s u l t i s q u i t e s i m i l a r t o t h o s e r e p o r t e d i n ( 2 ) . I n a l m o s t a l l t h e g l a s s e s c o n t a i n i n g K

O

t h e t e m p e r a t u r e dependence o f t h e r e s i s t i - v i t y c a n be r o u g h l y

'

3 r e ? r e s e n t c d by a single s t r a i g h t l i n e w i t h an a c t i v a t i o n e n e r g y i n c r e a s i n g t o 0.42-0.L1'7 eir a t

5-7

^{wt."; Cl} ₂ ⁰

3'

D i s c u s s i o n . - The a n a l y s i s o f

EP2

s p e c t r a o f barium-vanadate g l a s s e s c o n t a i n i n g i m p u r i t i e s o f f i v e d i f f e r e n t t r a n s i t i o n m e t a l o x i d e s show t h e c o n s i d e r a b l e i n t e r a c t i o n s between them and vanadium i o n s . It i s

C4-996 JOURNAL DE PHYSIQUE

essential that these interactions are different depending on an imp- urity. Some similar features can be found only for Pe203 and Mn203 impurities. Both oxides lead to broadening of hfs components of the

v4+ spectrum in the samples with low contents of Fea03 ancl k2o3.

Such behavior can be interpreted in terms of dipole-dipole interact- ions between vanadium

(4+)

ions and Fe or Mn ions. However, if the g=4.3 line indicates the presence of Pe3+ ions in the Fe-containing glasses, the valence states of Mn in the Mn-containing glasses are not known, The concentration dependence of the integrated intensity of EPR spectrum in Mn-BV glasses indicate the presence of Kramers' manganese ions (Mn2>h4:~n6~.1n the glass BV containing 5 wt.% Mn

0

2 3 the single line with g=2.018 was observed. It is known that.for fer- romagnetic coupling of two dissimilar ions S, and

S2

the pair g-va- lue is intermediate between those for the single-ions. On the contrary in the antiferromagnetic state there is an enhancement of the effectiveness of the ion with higher spin, and a contribution with reversed sign from the other ion. This fact allows the pair g- -values to lie outside the range of the single-ion values. It was shown that the effective g-value for pairs of ions of different spins (S7S2) in the case of antiferromagnetic coupling (3) is

g

[ S , + 1) g

1 - ^{sZg2J / (sl - S *} + I)

(1

It is easily seen that effective g=2.018 for ?km+-v4+ pair can be obtained only for gl>2, and S1= 5/2. Therefore, we assume that the line with g=2.018 is due to antiferromsgnetically coupled pairs Mn2+-lJ4+

(g1, S1

and

g * , S 2

refer

to

Mn2+

and V*+

respectively.

It is well known that cod+ ions are fast relaxing in oxide gl- asses and their EPR lines are too broad to be observed at temperat- ures as high as 300 or 77 K. The EPR spectrum of Co(2+) in oxide glasses has been detected only at 4.2 K

(4).

It consists of a single broad asymmetric line with g24. Ye assume that the majority of CO ions is in the co3+ state in the glasses of CO-BV seriss. Then the decrease, in the EPR signa of the V(4+) ions can be explained by electron transfer from 4' to co3+ in the mixed pair IT4+

^-0

- ^co3+.

The temperature dependence of the integrated intensity of EPR spect- rum of v4+ ions was used to estimate the magnitude of exchange ener-

gy

for this pair (251

2

130 cm-'. The line in low magnetic fields which appears at 77 K in glasses cf CO-BV series is possibly due to co2+ ions.

The sudden change in the EPR spectrum of v4+ ions at 35 C in the glasses of Cr-BV series can be presumably attributed to phase transition. This transition probably occurs in the vitreous phase since the shape of the spectrum and its hfs linewidths are characte- ristic of V(4+) in glasses.

References.

1. BOC.7"OLOVA L. D., GLASSOVA M.P., J. of Non-Crystalline S o l i d s 2 (1980) 423

2.

KAWAMOTO

Y.. TANIDA J., KAMADA H., J. Non-Crystalline Solids

(1980) 301

3. Md& E., VERA A., Z. Naturforsch (1976) 911

'

4.

BOGOMOLOVA L.D., LAZUKIN V.N., L'ETROVICII N.V., Doklady Akad-Nauk

SBSR, (1968) 314.