General equation of state for the pressure and temperature-induced transition in the ferroelectric triglycine selenate

An experimental investigation of the phase transition induced by temperatur e and pressure in the uniaxial ferroelectric triglycine selenate, which exh ibits a quasi-tricritical point at T-c approximate to 21.7 degrees C (at am bient pressure), has been performed. The combined pressure and temperature dependences of polarization versus electric field are shown to fit well by effective field theory using the general scaling combination [1 - (T/T-c p/p(c))] which involves temperature (T) and pressure (p), T-c being the tra nsition temperature at zero pressure and p(c) = -81.81 kbar the transition pressure extrapolated to zero absolute temperature. (C) 2000 Elsevier Scien ce B.V. All rights reserved.