Nucleation of domains under the influence of temperature in Ba5Ti2O7Cl4

It is found that the nucleation of domains can take place in Ba₅Ti₂O₇Cl₄ under the influence of temperature unlike in many other ferroelectrics. The nucleated domain can also be removed from the structure under the randomizing effect of temperature. These observations have been explained on the basis of a nucleation model of Ingle and coworkers suggested for KNbO₃. Similarity of physical situation in KNbO₃ and Ba₅Ti₂O₇Cl₄ regarding the existence of ordered point defects inducing nucleation of domains around them has been highlighted. This surprising similarity is suggested to be due to the physical processes occurring at the phase transition rather than due to any structural resemblance. The nature of nucleation occurring under the influence of temperature is shown to be identical with the nature of nucleation occurring under the influence of externally applied stress, and/or DC electric field. A new technique of identifying point defects responsible for nucleation of domains is reported.