THE INTERNAL FRICTION OF VANADIUM-PHOSPHATE GLASSES DOPED WITH BaO AND SrO

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THE INTERNAL FRICTION OF

VANADIUM-PHOSPHATE GLASSES DOPED WITH BaO AND SrO

D. Bednarczyk, W. Chomka, D. Samatowicz

To cite this version:

D. Bednarczyk, W. Chomka, D. Samatowicz. THE INTERNAL FRICTION OF VANADIUM- PHOSPHATE GLASSES DOPED WITH BaO AND SrO. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-439-C10-443. �10.1051/jphyscol:19851097�. �jpa-00225482�

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JOURNAL DE PHYSIQUE

Colloque C10, supplement au n012, Tome 46, d6cembre 1985 page C10-439

THE INTERNAL FRICTION OF VANADIUM-PHOSPHATE GLASSES DOPED WITH BaO AND SrO

D. BEDNARCZYK, W. CHOMKA and D. SAMATOWICZ

Technical University of Gdagsk, Department of Technical Physics and Applied Mathematics, Gdan'sk, Poland

ILbRtr.nt - ^Thevanadium-phosphate glasses of chemical composition XB.O

.

(50-x) v205 50 P o ^and^xSrO ^(50-9)v o *50p205

x from 10 to 50 rnol % were iHvfSstigated using the tgrflion pendulum at the frequency range 0,7 + 21 HE and at tempergtu- res between 120 and 650 K. The internal friction curve Q /T/

reveals the low-tempe ature m ximum connected with the electron relaxation between V+x and V+?. The influence of BaO and SrO on the relaxation process is studied. The activetion energy of this proceas increases from about 0 , 3 3 e V to 0.73 eV when x increases from 10 to 40 mol$. The low-temperature maximum slig- htly decreases and shifts to higher temperature when the con- tent of V 0 decreases from 50 to 10 mol$ and dis-apper in glasses withgut V 0 . ^Theactivation energies of internal friction low-t emperaturg &iximum are related to the activation energies for conductivity.

Oxide glacaes oontaixLmg t n w i t i o n metal ioas for imatanoe vanadium, ere electronically conductiga; eolide and they h v e eemiconductimg pro- perties. A general condition Tor semiconducting behavlour is that the transition metals lone should be capgtle of existing in more than one valence 6tat0,Por iggltaace ~ + 4 ard V ,ao that conduction can take place by the transfer of electrons from low to high valency states.

The tramport of electrom in those glasses is usual1 termed as small pclaron hopplng anfi c o n d u c t i o ~ ? has the character of tgermal activation process. One of the most interesting properties in thia kind of glasses is the electrical conductivity for which the activation energy i-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851097

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C10-440 JOURNAL DE PHYSIQUE

equal t o t h a t f o r d - i e l e c t r i c and mechanical r e l a x a t i o n /1,2/. The pur- pose of t h i s paper is t o r e p o r t experimental r e s u l t s on t h e influence of barium oxide and s t r o n t i u m oxid-e on t h e ~ - l / r / _ _ i n t h e vanadium- phosphate glasses. The first p a r t of s i m i l a r r e s u l t s vrith Ego and

CaO has been published e a r l i e r ] 3 /.

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Glasses were prepared by mixing proper amounts P O,,V,@ ,%O o r SrO.

Because E 0 i s s t r o ~ l y h y g r o e ~ o p i c diamonium $hbsph%e /I?H4Hqla WO was used gs5the s t a r t i n g luaterial, The well niixed composition w s mef- ted i n a porcelain c r u c i b l e a t 1573 f o r one hour i n a i r . The samples8 i n t h e form of t h i n rode 3f7 cm i n l e n g t h and 1+2,5 mm diameter we- r e drawn from t h e melt. The i n t e r n a l f r i c t i o n measurements were per- formed with t h e t o r s i o n pendulum technique w i n g t h e simple pendulum of Kd type as well a8 t h e i n v e - t e d pendulum i n a frequency range 0.5 t o 35 Hz under h e a t i n g t h e samples with t h e r a t e I K/min from I20 t o 700 K.

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Measurem$nts of $nternal f r i o t ion 0-l / T / and square of v i b r a t i o n f r e - quency f / T / (f is proportional t o s h e a r modulus G ) have been per- formed f o r two s e r i e s of g l a s s e s : xBaO* 50-x V 0 050 Z20 and ySrO*

50-y * V 05*50 P 0

.

The content of modifier &% and ~ r a ~ d e t e r m i n e d i n mol o,ha8e been i%inged systematicly from 0 t o 50 mol% f o r both ae- r i e e . &emplary r e s u l t s f o r 10 Ba0.40 V205.50 p205 g l a s s a r e presented on Fig.1.

r n t e r 2 e l f r i c t i o n Q " / ~ /

and f /T/ i n 10 Ba0-40 V205 -50 P205.

Two curves artf obtained f o r t h e samples with d i f f e r e n t v i b r a t i o n f r e - quency. I n ^'^Q / T I s p e c t r y two maxima can be observed and they a r e accompanied by bends on f / T / curves. A t higher v i b r a t i o n frequency maxima a r e s h i f t e d t o higher temperatures.

I n t h e present paper t h e low-temperature maximum hast been exa- mined i n d e t a i l s . This maximum i a s t r i c t l y connected wdth t h e presen- ce of vanadium i n glass. The influence of BaO and SrO modifier oxides on t h e low-temperature maximum is presented on Fig.2 and 3. There a r e a l s o included t h e p r e c i s e chemical compositions of t e t e d g l a s s e s , d a t e m i n e d by chemical analysis. The frequencies f I= ^f ⁾^mea-

sured a t 20°C a r e s i m i l a r and s h i f t i n maxima P ~ ~ i 3 P ~ ~ ig780ifnected with t h e change of g l a s s composition.With t h e decreasing content of vanadium t h e temperature of m u d m u m i n c r e a s e s and avera e maximum height decreases. !rheas observations a r e i n agreement wfth t h e re- Y ~ O U Q I Y assume# i n t e r p e t a t i o n that t h e same process of charge $ran- s f e r between Y * ^and^V5+vanedim ions is responsible f o r t h e low-

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50SrO . 5 0 q o 5 3 - f20= 1.3 Hz

2 .39,5Sr0 .10.5 V2O550 3 ^O5

f20= 0.83 Hz

1 30,5Sr0 19,5V2o5 5 0 9 O5 294 BOO 20 6V2O5.50q%

203Sr0 297V2O5 50qO5

1 I I

200 300 400 500 200 300 400 500

T I K I T C K I

Fig.2. Temperature dependenye o f Fig.3. Temperature dependence internal friction 'Q /TI of internal friction Q -? /T/

in vanadium-phosphate gla- in vanadium-phosphate glasses with SrO modifier. eses with B a O modifier.

temperature maximum of internal friction in group of vanadium-phospha-

te / I / and vanadium-phosphate modified. with alkaline earth oxide gla-

sses / 3 /.

The calculated activation energy of the process increases with the decreasing content of vanadium - Table 1. The values of activatfon energy for lasses containing SrO are higher than for glaeses with the

f

same conten of EaO, Activation energies calculated from the mechanical losses are similar to those determined from electrice3 conductivi- t y / 4 / which con irms th .arssumption that the same process of electron hopping between

A+

and VS+ tone ie responsible for mechanical losses and 6.c. electrical conductivltg.

m e dependence bet en the average height of low-temperature maxi- mum urd the ratio O = PP/V for the glasses with 30 mol% of BaO, Sr0,CaO and IdgO and with 2ot8&k of U 0 is presented on Pig.4. Then the ratio c approaches 50$,i.e. when ?ha number of relaxators incoea- ses the maximum height increases.

2'he influence of modifier oxide on the temperature position of maximum at a given frequency/? H z / is presented on Pig.5.

The temperatures of maximum increase in sequence: barium,strontium, calclitm and ma nesium lass,which is connected with the crease in cation potentia6 )

.

^{h e}dependence of the value oi the activation ener u on the kind of modifier oxide is due to the different polari-

~ing~nifueusnces from the modifying cations. The influence of strontium

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(30-442 JOURNAL DE PHYSIQUE

TABLE 1. Summary of results Measured glasses

Fig.4. Dependence of hightof Pig.5. Dependence of tempe- low-temperatur maxi- rature of low-te~pe- mum with C = V$+/Vtotal. rature maximum with

cation potentialflp ion or? the electron hopping process is somewhat different then for the rest of ions, This assumption may be confirmed by the literature data which also indicate that the properties dependent on the energy or character of glass net bo dings do not change systenaticly as the cations are changed from Ng9' through E%a2f. From characteristics bond of phosphate glasses of MeO-P 0 /Me = Mg,Ca,Sr,E?a / type we know about extreme position of stront!$d-phosphat e glasses / 5 / .

In all tested vanadium-phosphate glasses the second high-tempe- rarture maxlmum appeaqat about 550 K. Becaye of its small height

(sometimes it is only'the slight berid on Q- /T/ curve ) the proper characteristics (E 2, are difficult to obtain. Similar maxlrnwn has been observea in o&e glassea and probably it is connected with pro- ton migration / 2 /.

In barium-phosphate glasses the small br$ad maximum can be observed at about 220 K ( E = 0,56 eV, Z,, - ^10' ^s)- ^Fig.3. The mobili- ty of barium ions in bhium-phosphate glass as revealed in that low- temperature maximum as well as the low covalency, of bonding of the barium cation in bariwn-metaphosphate ( 14% ) incTicate the ionic character of the maximum / 2 / . The small peak observed at 330 K in cal- cium-phosphate glass is likely to have the same character / 6 /,

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REFERENCES

/I/ Field M.B., J.Appl.Phy8. ,40,2628-2632 j1968 1.

/2/ Chomka, W. and Samatowicz D. Journ. of Cxyst .Solids 57,327-337 (1983). - - -.

/3/ S m t wicz .)I and Bedlurcsyk D, Journ. de Phys. C9,Mo 12,t. 44 (19839.

/4/ Henclik S. Diploma, Technical University, Gdafak (1 983).

A. Phys. Chem. GlasEies ,vo1.26 ,No 1 (1 983 1.

W. and Samatowicl; D. Act& Phys.Fol.,vol, A 61,117-122