EFFECT OF HYDROSTATIC-PRESSURE ON THE FERROELECTRIC PHASE-TRANSITION IN KH2ASO4

Effect of hydrostatic pressure on the ferroelectric phase transition in KH2AsO4 is studied by dielectric measurements. The temperature at which the dielectric constant epsilon(C) takes a peak value decreases with increasing pressure, and no peak is observed at 15.0 kbar. The anomaly of epsilon(C) becomes broader with pressure. The transition temperature determined from the peak of epsilon(C) is well represented by the equation T(C) = B(p(C)-p)1/2 which is one of the manifestation of quantum ferroelectricity. Here, the critical pressure p(C) is determined to be 14.8 kbar. Another critical behavior for the quantum ferroelectricity near the critical pressure (epsilon(C)-epsilon(C)infinity)-1 = DT2 is examined. It is found that epsilon(C) at 14.5 kbar well represents this relationship.