Evidence of proton beam irradiation compared to isotope effect

In this study, we obtained experimental results similar to the isotope substitution effect by using the proton irradiation of K(H_0.47D_0.53)₂PO₄ (DKDP) ferroelectric single crystals. Temperature dependence of dielectric constants showed that the ferroelectric phase to paraelectric phase transition temperature increased from 175 K to 195 K of approximately 20 K after the proton beam irradiation. It was observed that the vibration mode P(OD)₂ was changed from 893 to 884 cm^-1 in Raman spectroscopy. In ¹H Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) experiments, the isotropic chemical shift after proton irradiation decreased from 14.46 to 14.32 ppm, which is indicative of the change of the O-H...O the equilibrium distance of hydrogen bonds estimated as 1.60066 Å and 1.62228 Å before and after the proton irradiation, respectively. It was observed that the Full width at half maximum (FWHM) line width also decreased from 563 to 244 Hz in ¹H MAS spectral line shape, which is indicative of obeying the displacive phase transition model.