Internal friction techniques were used to study the interaction of protons with other defects in material which was doped with 2, 3 or 5%Nd. After saturation with protons, the compounds gave rise to 2 broad anelastic relaxation peaks near to 340K and 273K at 5800Hz; with activation energies centered at 0.63 and 0.51eV, respectively. By using defect symmetry arguments, it was established that the 273K peak resulted from the reorientation of Nd-OH pairs, while the 340K peak was probably due to the relaxation of higher-order Nd-OH clusters. The results showed, for the first time, that protons were associated with dopants in this material. The relaxation strength was found to depend upon the square of the dopant concentration. Thermodynamic analysis revealed that the number of associated protons which produced the relaxation peaks made up less than 10% of the total proton concentration. No anelastic relaxation peak was detected in off-stoichiometric A3(Ca1+xNb2-x)O9. It was concluded that the creation of negative charges by off-stoichiometry produced a different defect structure for protons than when dopants were introduced. Thus, the presence of dopants was essential for protons to be able to produce anelastic relaxation in perovskite-type oxides.

Y.Du: Journal of the Physics and Chemistry of Solids, 1994, 55[12], 1485-90