Anomalous behaviour of linear birefringence and strain in taap crystal

Abstract Linear birefringence and lattice parameters were measured for the ferroelectric telluric acid ammonium phosphate in the temperature range 200–340 K. It is shown that anomalous temperature behaviour of the linear birefringence increment δ(Δn1) induced by the ferroelectric phase transition can be attributed to the temperature change of the spontaneous strain e13.