Impact of Thermal Treatment on the Surface of Na0.5Bi0.5TiO3-Based Ceramics

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na0.5Bi0.5TiO3-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly bonded cubic-shaped grains are also found among the micrographs presented in various publications. The present paper shows that this different surface character in Eu-modified Na0.5Bi0.5TiO3 can be obtained through thermal treatment across a wide range of temperatures. At higher temperatures, remarkable growth of cubic-shaped grains on the surface is observed. This growth affects the grain size distribution on the surface more than it does within the bulk of a sample. Such micrographs cannot be used to characterise the microstructure of dense ceramics. Intensive growth of TiO2 inclusions at high thermal treatment temperatures is also observed, revealing substantial evaporation of Bi and Na from the surface of a ceramic sample, but not from its core part.

Структура и механизмы образования наноразмерных пленок примесного металла кобальта и никеля в монокристаллах LiF и MgF-=SUB=-2-=/SUB=-

It is investigated the thermal etching of LiF and MgF2 crystals with cobalt and nickel impurities by means of scanning electron microscopy and atomic force microscopy with using decorating. It is shown that impurity inclusions leave the crystal from dislocations. The differences between of thermal etching in vacuum and air atmosphere take place. The crystallographic oriented terraced etch pits are formed after exit of impurities from dislocations. The square thermal etch pits are formed after thermal etching at 750°C in air. The surface impurity nanoscale film is formed at thermal etching. The oxidation of surface impurities observed at thermal etching in air atmosphere or in residual air atmosphere.