Mahmoud OMARI, Ilhem CHADLI, Salah BELAIDI

Defect structure and properties of Sr-doped $LaCrO_{3-delta}$

A defect chemical model for the behavior of acceptor-doped $LaCrO_{3-delta}$ as a function of oxygen pressure is proposed. This is considered within the regime that corresponds to oxygen deficit oxygen. The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of $La_{1-x}Sr_xCrO_{3-delta}$ in the range 0.10 < x < 0.30. The results show that the conductivity was independent of $pO_2$ and was proportional to the dopant concentration at high $pO_2$. Therefore, under reducing conditions, the conductivity decreased exponentially with decreasing $pO_2$ and asymptotically approached a $pO_2^{1/4}$ relationship. Stability regimes and compensation mechanisms at various oxygen partial pressures and temperatures are proposed. This model also examines the charge compensation mechanisms that dominate under the different regimes and their implications for transport properties. Prom equilibrium constants, thermodynamic quantities such as standard enthalpy and entropy change for the defect formation reactions were calculated.

PDF

___

1. H. Iwahara, T. Esaka and T. Sato, J. Solid State Chem., 39, 173 (1981).
2. M. Benkaddour, M. Omari, J.C. Boivin, P. Conflant and M. Drache, Ann. Chim. Sci. Mat. 25 (S1), 165 (2000).
3. F.W. Poulsen, Solid State Ionics, 129, 145 (2000).
4. J. Mizusaki, M. Yoshihiro,S. Yamauchi and K. Fueki , J. Solid State Chem., 67, 1 (1987).
5. M.H.R. Lankhorst, H.J.M. Bouwmeester and H. Verweij, Solid State Ionics, 96, 21 (1997).
6. E. Bakken, T. Norby and S. Stolen, J. Mat. Chem., 12, 317 (2002).
7. J. Mizusaki, S. Yamauchi, K. Fueki and A. Ishikawa, J. Solid State Chem., 12,119 (1984).
8. J. Faber, M. Mueller, W. Procarione, A. Aldred and H. Knott, Conference on High Temperature Science Related to Open Cycle, Cool Fired MHD Systems. Argonne National Laboratory, Argonne, IL, April 1977.
9. G. Spinolo and U. Anselmi-Tamburini, Ber. Bunsenges. Phys. Chem, 99 , 87 (1995).
10. G. Spinolo, U. Anselmi-Tamburini and P. Ghigna, Z. F¨ur Naturforschung, A52, 629 (1997).
11. F.W. Poulsen, J. Solid State Chem., 143 , 115 (1999).
12. D.B. Meadowcroft, Br. J. Appl. Phys., 9, 1225 (1969).
13. H. Uchida, H. Yoshikawa and H. Iwahara, Solid State Ionics, 35, 229 (1989).
14. Y. Larring and T. Norby, Solid State Ionics, 97, 523 (1997).
15. T. Schober and H. Wenzl, Ionics, 81, 111 (1995).
16. T. Schober, W. Schilling and H. Wenzl, Solid State Ionics, 86-88, 653 (1996).
17. F.A. Kröger and H.J. Vink, Solid State Physics, Vol. 3, p. 307, eds. by F. Seitz and D. Turnbull. Academic Press, New York, 1956.
18. B.A. Van Hassel, T. Kawada, N. Sakai, H. Yokokawa, M. Dokiya and H.J.M. Bouwmeester Solid State Ionics,66, 295 (1993).
19. I. Yasuda and T. Hikita, J. Electrochem. Soc., 140, 1699-1704 (1993).
20. H. Kamata, Y. Yononemura, J. Mizusaki, H. Tagawa, K. Naraya and T. Sasamoto, J. Phys. Chem. Solids,56, 943-50 (1995).
21. D.P. Karim and A.T. Aldred, Phys. Rev. B, 20, 1255 (1979).
22. J.B. Webb, M. Sayer and A. Mansingh, Can. J. Phys., 55, 1725 (1977).
23. J. Mizusaki, M. Yoshihiro, S. Yamauchi and K. Fueki, J. Solid State Chem., 58, 257 (1985).
24. M.H.R. Lankhorst, H.J.M. Bouwmeester and H. Verweij, J. Solid State Chem., 133, 555 (1997).
25. J. Mizusaki, Y. Mima, S. Yamauchi and K. Fueki , J. Solid State Chem., 80, 102 (1989).