Sintered (1475 degreesC/2 h) pellets of Ba(Zn1/3Ta2/3)O-3 were annealed at
temperatures ranging from 1550 to 1625 degreesC/15 h and subsequently quenc
hed into water. The degree of B-site order between the Zn and Ta cations wa
s investigated using x-ray diffraction (XRD) and transmission electron micr
oscopy (TEM). Samples quenched from 1575 to 1600 degreesC exhibit the, high
est degree of order by XRD. Dark-field TEM images from these samples reveal
ed 1:2, Zn:Ta, trigonal, ordered domains approximately 0.4 mum diam near gr
ain boundaries but 100 nm in the grain interior. Samples annealed and quenc
hed from 1625 degreesC exhibited no ordered superlattice reflections by XRD
. However, diffuse scatter along [111] directions and fee rather than trigo
nal ordered reflections were observed in electron diffraction patterns. Dis
ordered samples were subsequently annealed at 1500 degreesC/15 h (below the
order-disorder phase transition similar to 1625 degreesC) and +/-1/3{hkl}
superlattice reflections reappeared in XRD patterns demonstrating the rever
sibility of the phase transition. (C) 2000 American Institute of Physics. [
S0021-8979(00)03220-5].