Ordered structure formation in the flux-grown Ba(Mg1/3Ta2/3)O-3 single crystals

Formation of ordered structure in flux-grown Ba(Mg1/3Ta2/3)O-3(BMT) single crystals was studied using x-ray diffraction, electron diffraction, and hig h-resolution electron microscopy, The low-temperature-grown crystals exhibi ted no sign of B-site ordering. Annealing at 1500 degreesC induced the 1:2 ordered phase, and its content increased with the annealing time. The super lattice diffraction peaks were broad initially; they sharpened rapidly with the annealing time. Diffuse superlattice reflections were found in electro n diffraction patterns of 1500 degreesC annealed BMT; they turned into shar p reflections under long annealing time or higher temperature, 1600 degrees C. The intensity of diffuse reflections was sparsely distributed, but the m aximum intensity location was determined in the digitized recording of imag e plate. The maximum intensity sites of two diffuse reflections in the [111 ] direction deviated from the presumed 1/3 and 2/3 positions and shifted to wards the center. The diffuse reflection and the deviation from regular pos itions were interpreted as the composition modulation during B-site cation diffusion.