Proton Diffusion in Perovskite-Type Oxides Based on Small Polaron Model(Condensed Matter : Structure, Mechanical and Thermal Properties)

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The ground state energy and the wavefunction of proton in the cubic perovskite-type oxides ABO_3 are studied by using the double-well potential constructed from the one-dimensional O-H-O bond. We have found that when the O-O separation between the nearest neighbor oxygens becomes lower than 2.9A the proton wavefunction spreads over the double-well potential and the proton transfers between the minimum sites in the double-well potential. We have calculated the activation energy E_a for the proton transfer by using the small polaron model coupled with the lattice vibration of the O-B-O bond-bending mode. The calculated activation energy is found to be E_a=0.56eV for the cubic ABO_3. We have also found the B-atom mass dependence that E_a decreases with the B-atom mass in the O-B-O bond-bending mode. This B-atom mass dependence of E_a is similar to that shown in the deformed perovskite-type oxides ABO_3.
社団法人日本物理学会の論文
2005-11-15