EFFECT OF DEUTERATION ON SPONTANEOUS POLARIZATION OF KH2PO4 CRYSTALS

An accurate method of measuring the spontaneous polarization, which overcomes the problem of the long relaxation time was developed. The method is based on the possibility of releasing the spontaneous charge by heating the crystal through its Curie point. The values obtained are: Ps(KH2PO4) = 5·12 μ Coul cm2 and Ps(KH2PO4) = 6·15 μ Coul cm2. The difference is interpreted as resulting from the persistence of tunneling of the hydrogens in an asymmetric double minimum potential well. The asymmetry parameter was calculated to be B = 540 cm-1. A polarization tail above the Curie temperature was observed, and a picture of regenerative processes between imperfections and the dielectric behaviour of the medium is suggested. In crystals this effect may also cause a 'smearing' of phase transitions. © 1968.