Temperature dependences of the dielectric constant along the ferroelectric c-axis have been measured at various pressures up to 7. 9 GPa in KH
2PO
4 and KD
2PO
4. The vanishing of the ferroelectric state has been observed at 1. 7 GPa in KH
2PO
4 and at 6. 3 GPa in KD
2PO
4. The Curie constant C of KH
2PO
4 is almost independent of pressure. On the other hand, that of KD
2PO
4 above 4 GPa decreases about three fourths of that at atmospheric pressure. The crossover of the order-disorder type to the displacive one under high pressure is discussed on the mechanism of phase transition to explain these experimental results of KD
2PO
4.
抄録全体を表示