Birefringence Study of Ferroelectric Ordering in Oxygen Isotope Exchanged Systems SrTi(¹⁶O_1-<i>x</i>¹⁸O_<i>x</i>)₃

Abstract

An optical birefringence study was performed on the quantum ferroelectric phase transition in the oxygen isotope exchanged system SrTi( 16 O 1- x 18 O x ) 3 . The ferroelectric ordering in (110) c plates with the substitutional ratio x >0.33 brought about a marked enhancement in the temperature dependence of birefringence. The temperature derivative of the birefringence had a singularity at a temperature which can be regarded as the ordering temperature T c . The antiferrodistortive phase transition temperature T a of a (110) c sample with x =0.86 reached 107.7 K. The (001)-plane birefringence of a (110) c sample with x =0.83 exhibited a slight, but clear change at T c .