The chemical diffusivity of O in La0.79Sr0.20MnO3-x and La0.50Sr0.50Mn3-x was measured, in a solid-state electrochemical cell, by using the potentiostatic step method. At temperatures of between 700 and 860C, the chemical diffusivity of La0.79Sr0.20MnO3-x ranged from 10-8 to 10-6cm2/s (table 125). It was also markedly dependent upon O partial pressures of between 10-8 and 0.21atm. In the case of the stoichiometric material, the activation energy for O diffusion was 70kJ/mol. When La0.50Sr0.50Mn3-x was studied at temperatures of between 700 and 840C (table 126), the results were found to be essentially the same as those for the other material.
A.Belzner, T.M.Gür, R.A.Huggins: Solid State Ionics, 1992, 57[3-4], 327-37
Table 125
Self-Diffusion of O in La0.79Sr0.20MnO3-x
Temperature (C) | PO2 (atm) | D (cm2/s) |
700 | 2.8 x 10-2 | 3.1 x 10-12 |
700 | 2.7 x 10-4 | 4.7 x 10-12 |
760 | 2.1 x 10-1 | 1.5 x 10-11 |
760 | 2.3 x 10-3 | 2.4 x 10-11 |
760 | 2.6 x 10-5 | 1.6 x 10-11 |
760 | 2.8 x 10-7 | 1.2 x 10-11 |
780 | 5.2 x 10-2 | 4.0 x 10-11 |
815 | 7.5 x 10-2 | 5.8 x 10-11 |
815 | 5.8 x 10-2 | 4.2 x 10-11 |
815 | 8.2 x 10-4 | 1.9 x 10-11 |
860 | 2.1 x 10-1 | 1.4 x 10-10 |
860 | 3.4 x 10-3 | 7.4 x 10-11 |
860 | 5.7 x 10-5 | 3.5 x 10-11 |
860 | 9.3 x 10-7 | 9.7 x 10-12 |
700 | 2.1 x 10-1 | 4.5 x 10-12 |
700 | 8.3 x 10-2 | 4.4 x 10-12 |
760 | 2.2 x 10-1 | 2.2 x 10-11 |
Table 126
Self-Diffusion of O in La0.50Sr0.50MnO3-x
Temperature (C) | PO2 (atm) | D (cm2/s) |
750 | 2.1 x 10-1 | 2.1 x 10-12 |
750 | 8.5 x 10-2 | 2.2 x 10-12 |
750 | 3.5 x 10-2 | 3.4 x 10-12 |
785 | 1.6 x 10-1 | 7.0 x 10-12 |
800 | 2.2 x 10-1 | 1.3 x 10-11 |
800 | 8.9 x 10-2 | 1.2 x 10-11 |
830 | 2.6 x 10-1 | 1.7 x 10-11 |
695 | 2.8 x 10-2 | 3.3 x 10-13 |
750 | 8.6 x 10-2 | 3.1 x 10-12 |
780 | 1.4 x 10-1 | 4.0 x 10-12 |
800 | 9.0 x 10-2 | 8.1 x 10-12 |
820 | 2.1 x 10-1 | 7.6 x 10-12 |
820 | 9.1 x 10-2 | 4.5 x 10-12 |
820 | 3.9 x 10-2 | 3.8 x 10-12 |
820 | 1.7 x 10-2 | 2.3 x 10-12 |
820 | 7.4 x 10-3 | 3.5 x 10-12 |
840 | 1.9 x 10-1 | 1.5 x 10-11 |