Metal-like peak stress behavior of yttrium-doped BaCeO3 ceramic

Abstract

The high-temperature mechanical behavior of polycrystalline 5 at% yttrium-doped barium cerate with submicronic grain size (d = 0.5 µm) has been studied in compression between 1200 and 1300 °C at different initial strain rates. The true stress – strain curves display an initial peak stress followed by a softening stage and then by an extended steady-state stage; the magnitude of the peak stress is strongly dependent on strain rate and temperature. These characteristics are very similar to those found in metals and metallic alloys that exhibit dynamic recrystallization during creep at elevated temperatures. Microstructural observations by scanning and transmission electron microscopy have shown that the grain structure is progressively refined with increasing strain due to the strong interaction between dislocations and pre-existing twin boundaries, originated by the various crystal transformations that occur upon cooling from the sintering temperature. The empirical equations used in metals to describe the relationship between strain rate, peak stress, and peak strain are also valid in the present ceramic material.