Thermal and electric field induced phase transitions of Na0.5Bi0.5TiO3 single crystals

The phase transitions of unpoled and poled Na0.5Bi0.5TiO3(NBT) single crystals were studied using structural, hysteresis loops, polarizing-microscope, dielectric, mechanical (the first measurement), thermal expansion strain and calorimetric measurements. It was found that phase transitions in NBT are first-order and clearly demonstrate ferroelastic aspects. Both rhombohedral-tetragonal and tetragonal-cubic transformations are accompanied by a softening of mechanical properties like in improper ferroelastic transitions. It was concluded that the difference in the internal friction between unpoled/poled states and between [001](c)/[111](c) poled states can be associated with a difference in the density of mobile ferroelastic twin walls in these states. (C) 2022 Published by Elsevier B.V.

Automated summary

The phase transitions of unpoled and poled NBT single crystals were studied, and it was found that these transitions are of first-order and exhibit ferroelastic aspects. The transformations between rhombohedral-tetragonal and tetragonal-cubic phases result in a softening of mechanical properties, similar to improper ferroelastic transitions. The difference in internal friction between unpoled/poled states and between different poled directions can be attributed to the density difference of mobile ferroelastic twin walls.