THE ROLE OF ORDERED A(1)-SITE VACANCIES IN BELT NANO-DOMAINS OF PB1-XBAXNB2O6 (PBN) SOLID-SOLUTION

The order-disorder states of the A-site vacancy of PEN solid solution affected by different thermal treatments were studied with the aid of High Resolution Electron Microscopy (HREM). PBN ceramics around the mo rphotropic phase boundary were prepared through two routes to control ordering degree of the A-site vacancy: (1) samples through quenching p rocesses resulted in chaotic states of the A-site vacancies and misfit anti-phase boundary; (2) samples through slow cooling led to an order ed structure of the vacancies in the A(1)-site. The ordered Al-site va cancies were modulated by interchanges of the sublattices of the order ed vacancies and the Pb2+ cations in the A(1)-sites along both [(1/2) over bar 00](p) and [0 (1/2) over bar 0](p) orientations, forming a na rrow discommensurate wall between two anti-phase domains, The anti-pha se domains were observed as a regular belt structure with dimensions o f about 45 nm x (greater than or equal to 120) nm. The belt nano-domai n structures were a result of quasi-equilibrium thermodynamic processe s.