Structural phase transitions of Na(DxH1–x)3(SeO3)2 single crystals studied by observation of H2 and N23a nuclear magnetic resonance

Abstract

Na ( D x H 1 – x ) 3 ( SeO 3 ) 2 single crystals were grown with a deuterium content of 37%, and the spectra and relaxation times of the H2 and N23a nuclei in the mixed Na(D0.37H0.63)3(SeO3)2 crystals were measured as functions of temperature. The H2 and N23a nuclear magnetic resonance (NMR) spectra undergo changes near 213 K. Our N23a NMR results for x≥0.3 show that there is no triclinic intermediate phase; the paraelectric α-phase and ferroelectric γ-phase arise in mixed Na(D0.37H0.63)3(SeO3)2 crystals. In addition, the H2 and N23a relaxation times of mixed Na(D0.37H0.63)3(SeO3)2 crystals are different from the H2 and N23a relaxation times of NaH3(SeO3)2 and NaD3(SeO3)2. The effects of partial deuteration of sodium trihydrogen selenite crystals include not only a shift in the phase transition temperature TC but also a change in the local symmetry.