Structural phase transitions in partially deuterated betaine phosphite crystals studied by dielectric and electron paramagnetic resonance methods

Ultrasonic Anomalies in Deuterated Betaine Phosphite near the Ferroelectric Phase Transition

“…This isotope effect has been already studied in deuterated crystals of the betaine family as betaine phosphate (DBP) and betaine phosphite (DBPI) [6, 10 to 13]. The low frequency dielectric measurements of DBPI showed [12,13] that the ferroelectric transition is shifted to 297 K. EPR studies revealed that the ferroelectric phase transition is related to the simultaneous ordering of deuterons in the O±D F F F O bonds [14]. The dielectric behaviour of deuterated betaine phosphite crystals has been investigated in the frequency range up to 4 GHz.…”

Anomalies of the Low Frequency Dielectric Dispersion in Betaine Phosphite

“…A further structural transition at Tc3 = 177 K [l] is suspected. There are hints to the fact that the high temperature phase transition is related to the order behaviour of the betaine molecules [4] and to tiltings of the PO3 groups [5] but is not connected with an ordering of the protons in the 0-H.. .O bonds [6]. Dielectric measure- ments [3] and electron nuclear double resonance [7,81 (ENDOR) showed that the transition in the ferroelectric ordered state is connected with the order behaviour of the protons in the O-H.. .O bonds.…”

Ferroelectric Thin Films of Betaine Phosphite, Glycine Phosphite and of Their Deuterated Analogs

“…P 2 1 , Z = 4) at Т с ∼ (200-225) K with spontaneous polarization along the b axis [14,15]. The ferroelectric phase transition temperature of BPI can be increased up to Т с ∼ 310 K by deuteration, i.e., by replacing hydrogen ions H + , which form hydrogen bonds between HPO 3 tetrahedrons in the structure of the BPI crystals, with deuterium ions D + [16,17]. The transition into the ferroelectric state is followed by a strong dielectric anomaly with the maximum dielectric permittivity as high as 10 4 .…”

“…In the crystal structure of partially deuterated BPI crystals, both hydrogen H + and deuterium D + ions are statistically distributed in crystallographic positions, and the ferroelectric phase transition temperature T c linearly depends on the deuteration degree D (T c ∼ 220 K for D = 0, and T c ∼ 310 K for D = 100%) [16,17]. Such an isotopic effect has also been observed in betaine phosphate (BP), betaine arsenate (BA) [2], and glycine phosphite (GPI) single crystals [18] which have the crystal structure characterized by zig-zag chains of oxygen tetrahedrons connected by hydrogen bonds which is similar to that of BPI [19][20][21].…”