Significant increase of the ferroelectric phase transition temperature in partially deuterated KH_2PO_4 by proton irradiation

摘要

The ferroelectric phase transition temperature was significantly raised by 5 K in partially deuterated KH_2PO_4 irradiated by a proton beam. Increase in the hydrogen bond length was indicated by the dielectric constant analysis. Deuteron nuclear magnetic resonance (NMR) measurements of the electric field gradient tensor showed atomic displacement after the proton irradiation, and ~(31)P NMR measurements of the chemical shift tensor revealed phosphorous displacement in the hydrogen-bonded direction and the PO_4 tetrahedral distortion. Increase of the phase transition temperature can be closely related to the structural modification involving the hydrogen-bond geometry.