Grain boundary grooving by surface diffusion in SrTiO₃ bicrystal

Abstract

High-purity SrTiO3 bicrystal sample (the angle between two [001] directions is 24°) was used in the present experiment to develop a thermal grain boundary groove along the bicrystal grain boundary at different temperatures (1150–1400 °C) and times (15–6720 min) in air. An atomic force microscope (AFM) was used to observe the surface morphological change in the annealed bicrystal sample in order to measure the width W and depth h of the developed grain boundary groove. It was found that the log W–log t (at 1150–1400 °C) and the log h°log t (at 1400 °C) relationships are approximately linear, having slopes of approximately 1/4. Using Mullins' formulas, the surface diffusion coefficients of SrTiO3 at different temperatures were calculated. Finally, the surface diffusion coefficient determined in the present experiment appears to correspond to the titanium atom, which has the lowest diffusivity in SrTiO3.

Grain-boundary grooving by surface diffusion with asymmetric and strongly anisotropic surface energies

“…[4][5][6][7] When the temperature is high and the surface energy is isotropic, the groove profile is smooth and agrees well with Mullins's solution. In a typical experi-ment, the groove width and height are measured as functions of time and compared with Mullins's model to extract the surface diffusion coefficient.…”

“…In a typical experi-ment, the groove width and height are measured as functions of time and compared with Mullins's model to extract the surface diffusion coefficient. 7 If a polycrystalline solid is used to form grooves, then the groove profiles are almost always asymmetric. 7,8 However, when the surface energy is anisotropic at low temperatures, facets begin to appear on the groove surface.…”

Sr diffusion in undoped and La-doped SrTiO3single crystals under oxidizing conditions

“…A verification using experimental data from the literature is difficult. Up to now, no Sr vapour pressure data is available for SrTiO 3 and only one study on surface diffusion on SrTiO 3 was published, 39 where the deepening of a grain boundary groove was measured by atomic force microscopy and therefore only the diffusivity of the slowest species, in the case of SrTiO 3 Ti, was determined. Also, the restructuring of the surface accompanied by a secondary phase growth (see section 1) leads to changes and local variations in the activities of Sr and Ti containing species at the surface making thermodynamical calculations based on vapour pressure data of SrO and TiO 2 highly speculative.…”

Remnant grooves on alumina surfaces

“…The theory predicts two surface maxima, one on each side of the groove. These ridges have been observed experimentally in W [11,12], Fe [13], Pd [14], NiAl [15], Al 2 O 3 [16][17][18], ZrO 2 [19], SrTiO 3 [20], and CeO 2 [21]. MullinsÕ theory describes the development of a thermal-grain-boundary groove by surface diffusion and allows surface diffusion coefficients to be deduced from the geometries of grain-boundary grooves:…”