Formation of snowflake domains during fast cooling of lithium tantalate crystals

Formation of the original dendrite snowflake-shape domains during fast cooling after heating above phase transition temperature by pulse laser irradiation was revealed in congruent lithium tantalate crystals. The effect was attributed to polarization reversal under the action of spatially nonuniform pyroelectric field. Two stages of the domain shape evolution at the surface were separated: (1) growth of circular domains by sideways motion of the domain walls and (2) backswitching leading to formation of the snowflake domains. The simulated spatial distribution of the pyroelectric field in regular two-dimensional structure was used for an explanation of the obtained results. The backswitching process in the surface layer has been attributed to change of the sign of the pyroelectric field at the domain wall. The snowflake domain shape is caused by the formation of isolated nanodomain fingers and hampering of their merging.