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Solid state electrochemical cell
Progress
in
Crystal Growth
PERGAMON
and Characterization Progress in Crystal Growth and Characterization of Materials of Materials (2002) 139-141 http://www.elsevier.com/locate/pcrysgrow
Solid State Electrochemical
Cell
V.Venugopal, Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085. Abstract
In recent years, the growing interest in new aspects of energy technology has provided a strong stimulus for the investigation and development of many of these electrolytes. Widespread interest in rechargeable cells has resulted in the development of a number of high-energy battery systems. The sodium-sulphur battery with p-alumina cerami’c (Na (l)/@alumina/Na~S.) as the electrolyte belongs to this class [l]. Amongst the spectrum of energy conversion devices, solid oxide electrolytes have found use in electrochemical (fuel cell), thermoelectric and magnato hydrodynamic generator [2] and in miniature primary cells [3]. The growing demand for materials for application_ at high temperatures in nuclear technology stimulated interest in a systematic investigation of the thermodynamic properties of nuclear fuel related systems. Solid electrochemical cells are used extensively in DAE for thermodynamic investigation and in sensor development. These aspects will be covered in the talk. Key words: Electrolytes, Cells, Alumina, Thermoelectrics, Zirconia, Yttria and Thoria
1. Introduction Properties of Solid electrolytes
Useful solid electrolytes have the fluorite crystal structure and abnormally high oxygenion conductivities. This structure is rather open one and rapid ion diffusion might be expected. The three most frequently used solid electrolyte for emf measurements are calcia stabilize zirconia (CSZ), yttria doped thoria (YDT) and CaF2 [3,4,5]. The predominant use of solid electrolytes for emf measurements of thermochemical data originates from the work of Klukkola and Wagner [6]. Wagner has derived the relation between the electromotive force(E) of an electrochemical cell and the chemical potential( p) at each electrode: till E= -l/(nF) 1 t(ion) dp @) Where F is Faradays Constant, n is the absolute value of the valency of the ion in the electrolyte, p(1)+(2), t(ion) is the ionic transference number, which is the fraction of current carried by ionic carriers. For an oxide electrolyte t(ion)=l and above equation reduces to AG= p(1)+(2) =-nFE In case where t(ion) differs significantly from unity, corrected values of E may sometimes be obtained if transference numbers are known. Such corrections were made 0960-8974/02/$ - see front matter Q 2002 Published by Elsevier Science Ltd. PII: SO960-8974(02)00039-6
140
K Venugopal/
Prog. Crystal Growth and Charact. 45 (2002) 139-141
by Denlect et al [7]. Treatment of this problem was made by Schmalzried’s theoretical analysis [8] of mixed ionic and electronic conduction in oxygen-ion conductors. Gibbs Energy of Formation of oxides Oxide electrolyte Thermodynamic studies of compounds in Na-MO-O; Na-Cr-0, Ba-MO-O, Ba-U-O, SrMO-O, Cs-U-O ar;l r?b-1.W SWI:III, tve important role in life determination of the clad in an operating nk:!L‘i: .x.,Lc‘. :I XL;,.,te standard Gibbs energy of formation values of number of oxides in these system have been obtained from emf measurements, using a galvanic cell with a suitable reference electrode. One of such typical cell can be represented by SrMoOs(s)+SrMoOh(s)
]CSZ (solid electrolyte)
1 Ni(s)+NiO(s)
From a knowledge of the oxygen pressure at the reference electrode NiO(s)+Ni(s), the oxygen pressure in equilibrium with SrMoO$s)+SrMo04(s) at experimental temperature is known from measured E and hence standard Gibbs energy of formation of SrMoOd(s) can be calculated. Using the similar types of cell A@(T) values for BaaUaOrr(s), BaUaO-i(s), NazMoOe(s), Na2Moz07(s), NaaMosOta(s), Na&fO@&), BaMoOd(s), Rb~U~Or~(s),Rb~U~Ot~,UTeO&aFe03 and BaMoaO7(s), NaCrOz(s), CsCrzO7(s), LaCoOa,La&oaOta and LaaCoO4 have been determined in our lab [ 9-131. Fluoride Electrolyte Fluoride electrolytes have been successfully used for thermodynamic determination due to its ability to measure at low partial pressure of oxygen. cell involving oxides of thorium and CaF2 electrolyte can be represented as:
(-)Pt,02/SrO(s)+SrF2(s)//CaF2//(SrTh03(s)+~O~(s)+SrF2(s)/O~,Pt(+)
(1)
The net cell reaction is: SrO(s) + ThOz(s) = SrThOa(s)
(4)
property A typical
The emf of the cell gives the Gibbs energy change of the reaction. [14]. Using the similar type of cell A@‘(T) of SrRuOa(s) has been measured. Calcium fluoride has also been employed in the thermodynamic investigations of carbides and borides of Th, U, Mn and Cr. The typical configurations are Pt, Th+ThS
( CaFz ( ThF4+ThCz+C,Pt
2. Activity measurement
and Phase Diagram
The activity of the least stable metal can be measured in binary and multicomponent systems at temperatures as low as 1000 K. In our lab activity of Ni was determined employing a cell with oxide electrolyte and the cell is given as:
1! Venugopal/
Prog. Crystal Growth and Char-act. 45 (2002) 139-141
141
Pt, Au, Nio.sc,sTeo.has (s)tNiO(s) ( CSZ ( air, Au, Pt The observed emf E of the cell directly gives the activity aN, of the alloy, Nia.sssTer,.&s). Combining the Knudsen cell with galvanic cell, activity of both the components can be found out [lS].The thermodynamics of oxygen dissolved in metals is vital to metallurgists because the physical properties of many metals and alloys are greatly influenced by the amount of oxygen present. Solid oxide electrolyte galvanic cells are very suitable to determine quantitatively and dissolvr j (<‘,‘““‘, . , I,,:t;)i; ad alloys. Using similar type of cell with YDT electrolyte, oxygen di:Li:j,j,s;,i i I ~z;Gti +>drGln Coolant can be found out. Kubaschewski [16] has discussed at length the advantages of constructing equilibrium diagrams from Gibbs energy data. The solid electrolyte method yields directly the Gibbs energy mixing and hence is finding increasing application in alloy themochemistry. A discontinuity in the emf versus composition plot indicates a possible intermetallic phase or a miscibility gap. If a number of intermetallic phases exist in the system, by appropriate choice of the electrode systems, Gibbs energy information of all of them could be determined.
References 1. N.K. Gupta and R.P Tischer, J. Electrochem Sot. 119 (1972) 1033. 2. J.O.M. Bockris and S., Srinivasan, Fuel-cells-their Electrochemistry, McGraw Hill, New York, 1969. 3. E.C. Subbarao, Solid Electrol;yte und their applications, Plenum Press, New York and London, 1980. 4. J.N. Pratt, Metallurgical Transactions A, 21 A (1090) 1223. 5. T.H. Etsell and N. Flengas, 70 (1970) 339. 6. C. Wagner, Z.Phys. Chem., 21 (1 Y33) 25. 7. J. Delect, A. Delgado Brune and J.J. Egan, Calculation of phase diagrams and thermochemistry of alloy phases, Proc Symp. AIME, Y.A. Chang and J.F Smith eds. TMS-AIME warrendale PA, 1979 p-275. 8. H.Schmalzried, Z. Phys. Chem., N.F. 38 (1963) 87. 9. R Prasad, VS. Iyer, V. Venugopal, Ziley Singh and D.D. Sood, J. Chem. Thermody, 19 (1987 ) 613. 10. V.S. Iyer, V.Venugopal and D.D. Sood , J. Radio. Nucl. Chem., 143 (1990) 157. 11. V. Venugopal, VS. Iyer, V. Sundaresh, Ziiey Singh, R. Prasad and D.D. Sood., J. Chem. Thermody., 19 (1987) 19. 12. V. Venugopal, V.S. Iyer, R. Agarwal, K.N. Roy, R. Prasad and D.D. Sood., J. Chem. Thermodyn., 19 (1987) 1047. 13. Ziley Singh, Smruti Dash, Rajendra Prasad and D.D. Sood, J. Alloys and Comp., 215 (1994) 303. 14. R. Prasad, Smruti Dash, S.C. Parida, Ziley Singh and V.Venugopal, Wotkshop cum Seminar on Electroanalytical Chemistry and Allied Topics, Nov.27- Dec.1, 2000. 15. J. Hladik,Physics of Electrolytes (~01-2) Academic Press London, New York,1972. 16. 0. Kubaschewski, Naturwisseen Schaften, 55 (1968)525.
in
Crystal Growth
PERGAMON
and Characterization Progress in Crystal Growth and Characterization of Materials of Materials (2002) 139-141 http://www.elsevier.com/locate/pcrysgrow
Solid State Electrochemical
Cell
V.Venugopal, Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085. Abstract
In recent years, the growing interest in new aspects of energy technology has provided a strong stimulus for the investigation and development of many of these electrolytes. Widespread interest in rechargeable cells has resulted in the development of a number of high-energy battery systems. The sodium-sulphur battery with p-alumina cerami’c (Na (l)/@alumina/Na~S.) as the electrolyte belongs to this class [l]. Amongst the spectrum of energy conversion devices, solid oxide electrolytes have found use in electrochemical (fuel cell), thermoelectric and magnato hydrodynamic generator [2] and in miniature primary cells [3]. The growing demand for materials for application_ at high temperatures in nuclear technology stimulated interest in a systematic investigation of the thermodynamic properties of nuclear fuel related systems. Solid electrochemical cells are used extensively in DAE for thermodynamic investigation and in sensor development. These aspects will be covered in the talk. Key words: Electrolytes, Cells, Alumina, Thermoelectrics, Zirconia, Yttria and Thoria
1. Introduction Properties of Solid electrolytes
Useful solid electrolytes have the fluorite crystal structure and abnormally high oxygenion conductivities. This structure is rather open one and rapid ion diffusion might be expected. The three most frequently used solid electrolyte for emf measurements are calcia stabilize zirconia (CSZ), yttria doped thoria (YDT) and CaF2 [3,4,5]. The predominant use of solid electrolytes for emf measurements of thermochemical data originates from the work of Klukkola and Wagner [6]. Wagner has derived the relation between the electromotive force(E) of an electrochemical cell and the chemical potential( p) at each electrode: till E= -l/(nF) 1 t(ion) dp @) Where F is Faradays Constant, n is the absolute value of the valency of the ion in the electrolyte, p(1)+(2), t(ion) is the ionic transference number, which is the fraction of current carried by ionic carriers. For an oxide electrolyte t(ion)=l and above equation reduces to AG= p(1)+(2) =-nFE In case where t(ion) differs significantly from unity, corrected values of E may sometimes be obtained if transference numbers are known. Such corrections were made 0960-8974/02/$ - see front matter Q 2002 Published by Elsevier Science Ltd. PII: SO960-8974(02)00039-6
140
K Venugopal/
Prog. Crystal Growth and Charact. 45 (2002) 139-141
by Denlect et al [7]. Treatment of this problem was made by Schmalzried’s theoretical analysis [8] of mixed ionic and electronic conduction in oxygen-ion conductors. Gibbs Energy of Formation of oxides Oxide electrolyte Thermodynamic studies of compounds in Na-MO-O; Na-Cr-0, Ba-MO-O, Ba-U-O, SrMO-O, Cs-U-O ar;l r?b-1.W SWI:III, tve important role in life determination of the clad in an operating nk:!L‘i: .x.,Lc‘. :I XL;,.,te standard Gibbs energy of formation values of number of oxides in these system have been obtained from emf measurements, using a galvanic cell with a suitable reference electrode. One of such typical cell can be represented by SrMoOs(s)+SrMoOh(s)
]CSZ (solid electrolyte)
1 Ni(s)+NiO(s)
From a knowledge of the oxygen pressure at the reference electrode NiO(s)+Ni(s), the oxygen pressure in equilibrium with SrMoO$s)+SrMo04(s) at experimental temperature is known from measured E and hence standard Gibbs energy of formation of SrMoOd(s) can be calculated. Using the similar types of cell A@(T) values for BaaUaOrr(s), BaUaO-i(s), NazMoOe(s), Na2Moz07(s), NaaMosOta(s), Na&fO@&), BaMoOd(s), Rb~U~Or~(s),Rb~U~Ot~,UTeO&aFe03 and BaMoaO7(s), NaCrOz(s), CsCrzO7(s), LaCoOa,La&oaOta and LaaCoO4 have been determined in our lab [ 9-131. Fluoride Electrolyte Fluoride electrolytes have been successfully used for thermodynamic determination due to its ability to measure at low partial pressure of oxygen. cell involving oxides of thorium and CaF2 electrolyte can be represented as:
(-)Pt,02/SrO(s)+SrF2(s)//CaF2//(SrTh03(s)+~O~(s)+SrF2(s)/O~,Pt(+)
(1)
The net cell reaction is: SrO(s) + ThOz(s) = SrThOa(s)
(4)
property A typical
The emf of the cell gives the Gibbs energy change of the reaction. [14]. Using the similar type of cell A@‘(T) of SrRuOa(s) has been measured. Calcium fluoride has also been employed in the thermodynamic investigations of carbides and borides of Th, U, Mn and Cr. The typical configurations are Pt, Th+ThS
( CaFz ( ThF4+ThCz+C,Pt
2. Activity measurement
and Phase Diagram
The activity of the least stable metal can be measured in binary and multicomponent systems at temperatures as low as 1000 K. In our lab activity of Ni was determined employing a cell with oxide electrolyte and the cell is given as:
1! Venugopal/
Prog. Crystal Growth and Char-act. 45 (2002) 139-141
141
Pt, Au, Nio.sc,sTeo.has (s)tNiO(s) ( CSZ ( air, Au, Pt The observed emf E of the cell directly gives the activity aN, of the alloy, Nia.sssTer,.&s). Combining the Knudsen cell with galvanic cell, activity of both the components can be found out [lS].The thermodynamics of oxygen dissolved in metals is vital to metallurgists because the physical properties of many metals and alloys are greatly influenced by the amount of oxygen present. Solid oxide electrolyte galvanic cells are very suitable to determine quantitatively and dissolvr j (<‘,‘““‘, . , I,,:t;)i; ad alloys. Using similar type of cell with YDT electrolyte, oxygen di:Li:j,j,s;,i i I ~z;Gti +>drGln Coolant can be found out. Kubaschewski [16] has discussed at length the advantages of constructing equilibrium diagrams from Gibbs energy data. The solid electrolyte method yields directly the Gibbs energy mixing and hence is finding increasing application in alloy themochemistry. A discontinuity in the emf versus composition plot indicates a possible intermetallic phase or a miscibility gap. If a number of intermetallic phases exist in the system, by appropriate choice of the electrode systems, Gibbs energy information of all of them could be determined.
References 1. N.K. Gupta and R.P Tischer, J. Electrochem Sot. 119 (1972) 1033. 2. J.O.M. Bockris and S., Srinivasan, Fuel-cells-their Electrochemistry, McGraw Hill, New York, 1969. 3. E.C. Subbarao, Solid Electrol;yte und their applications, Plenum Press, New York and London, 1980. 4. J.N. Pratt, Metallurgical Transactions A, 21 A (1090) 1223. 5. T.H. Etsell and N. Flengas, 70 (1970) 339. 6. C. Wagner, Z.Phys. Chem., 21 (1 Y33) 25. 7. J. Delect, A. Delgado Brune and J.J. Egan, Calculation of phase diagrams and thermochemistry of alloy phases, Proc Symp. AIME, Y.A. Chang and J.F Smith eds. TMS-AIME warrendale PA, 1979 p-275. 8. H.Schmalzried, Z. Phys. Chem., N.F. 38 (1963) 87. 9. R Prasad, VS. Iyer, V. Venugopal, Ziley Singh and D.D. Sood, J. Chem. Thermody, 19 (1987 ) 613. 10. V.S. Iyer, V.Venugopal and D.D. Sood , J. Radio. Nucl. Chem., 143 (1990) 157. 11. V. Venugopal, VS. Iyer, V. Sundaresh, Ziiey Singh, R. Prasad and D.D. Sood., J. Chem. Thermody., 19 (1987) 19. 12. V. Venugopal, V.S. Iyer, R. Agarwal, K.N. Roy, R. Prasad and D.D. Sood., J. Chem. Thermodyn., 19 (1987) 1047. 13. Ziley Singh, Smruti Dash, Rajendra Prasad and D.D. Sood, J. Alloys and Comp., 215 (1994) 303. 14. R. Prasad, Smruti Dash, S.C. Parida, Ziley Singh and V.Venugopal, Wotkshop cum Seminar on Electroanalytical Chemistry and Allied Topics, Nov.27- Dec.1, 2000. 15. J. Hladik,Physics of Electrolytes (~01-2) Academic Press London, New York,1972. 16. 0. Kubaschewski, Naturwisseen Schaften, 55 (1968)525.