Order and disorder of the A-site vacancies in solid solutions were studied by means of high-resolution electron microscopy. It was found that ceramic samples that were prepared by quenching exhibited chaotic arrangements of the A-site vacancies, and misfit antiphase boundaries. Samples which were prepared by slow cooling exhibited an ordered arrangement of vacancies on the A1-sites. The ordered A1-site vacancies were modulated by interchanges of the sub-lattices of the ordered vacancies, with Pb2+ cations in the A1-sites, to form a narrow discommensurate wall between 2 antiphase domains. The antiphase domains were seen as regular belt structures, with dimensions of about 45nm x 120nm. The belt-like nano-domain structures were attributed to quasi-equilibrium thermodynamic processes.

X.Xiaoa, Y.Xu, Z.Zeng, Z.Gui, L.Li, X.Zhang: Journal of Materials Research, 1996, 11[3], 650-6