Birefringence Study of a Phase Transition in TGS Crystals

Abstract Accurate measurements of the optical birefringence over the temperature range 20–80°C have been made for the uniaxial ferroelectric triglycine sulfate (TGS) along the ferroelectric b‐axis. An anomaly at the Curie temperature is clearly seen. A slight deviation from Landau‐like behaviour is observed in the temperature range 0°C ≤ T – T c ≤7°C, which is in agreement with recently obtained results on the dielectric, thermal and elastic properties.