Abstract: With the size decreasing, a ferroelectric will change from multi-domain to single-domain and then from ferroelectric to paraelectric. The size at which a ferroelectric changes from muti-domain to single-domain is called the single-domain critical size, and the size below which ferroelectricity disappears is called the ferroelectric critical size. In this work, we calculated the two critical sizes for barium titanate and lead titanate respectively. The calculated results accord with experimental.

Key words: single-domain critical size, ferroelectric critical size, barium titanate, lead titanate