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Quantum paraelectricity in KD2PO4 and KH2PO4 under high pressure
Shoichi Endo1, Kiyoshi Deguchi, Masaharu Tokunaga
1Research Center for Material Science at Extreme Conditions, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Abstract:
Phase transition temperatures of hydrogen-bonded ferroelectrics DKDP ( KD2PO4) and KDP ( KH2PO4) vanish at pressure p larger than respective critical pressures p(c). The dielectric constants epsilon(c) has been observed to be suppressed with decreasing temperature for p>p(c) and analyzed as the quantum paraelectricity by fitting with the Barrett formula in terms of three parameters. The dependences of the three parameters on p-p(c) are found to be expressed by almost similar lines, and the phase transition mechanism near p(c) is explained from the viewpoint of an anharmonic phonon system in KDP and DKDP.