Dielectric Dispersion in Ferroelectric Glycine Phosphite

Abstract

Dielectric dispersion in ferroelectric hydrogen bonded glicyne phosphite crystal was investigated in the frequency range 100 Hz -27 GHz. Dielectric relaxation of Debye type observed in the paraelectric phase shows a critical slowing down of the polarization fluctuations. The relaxation frequency decreases with temperature according to fs = 0.305(Τ -Τ0) GHz in the paraelectric phase. The activation energy for flipping dipole motion ΔU = 2.07kΤc confirms order-disorder character of the phase transition. In the ferroelectric phase pronounced low frequency (100 Hz -1 MHz) dispersion related to domain contribution to permittivity was found.

Ultrasonic Studies of Ferroelectric Phase Transition in Gly-H3PO3 Crystals

“…3), we have determined the soft mode relaxation time t. The temperature dependence of the inverse relaxation time T -1 in the ferroelectic phase is presented in the insert of Figure 3. In the temperature region T C -2^T C -0.3 K it can be linearly fitted as z~1 =(T C -T)/r 0 , where t 0 = (6.3 ±0.5) x 10" 10 K s. The obtained value of t 0 is close to the one determined from the dielectric measurements (r o = (4.2±0.5) x 10" 10 K s [7]). Thus, we see that the condition Q r 1 mentioned above is valid.…”

Proton Ordering Model of Phase Transitions in Hydrogen Bonded Ferrielectric Type Systems: The Gpi Crystal

“…A large anomaly of permittivity in the c-direction has also been detected; at room temperature ε c is higher than ε b [7]. Apart from the structure investigations, the measurements of frequency dependence of dielectric constant also lead to the conclusion that the phase transition in GPI is of the order-disorder type [8,9]. However, the observed dynamics of the soft relaxational mode connected with the proton flipping in the double potential well is more complicated in GPI than in the other similar H-bonded ferroelectrics (for example, BPI).…”

Dynamic properties of NH_3CH_2COOH·H_2PO_3 ferroelectric

“…The effective dipole moments in the paraelectric phase are equal to µ x 13 = 0.4 · 10 −18 esu·cm; µ In [9] the transition temperature is T c = 223.6 K, and one should multiply the parameters w 0 , ν 0± f , δ i , ψ ± f i , µ i 13 , µ i 24 by the coefficient 0.994. The volume of a primitive cell of GPI is υ = 0.601 · 10 −21 cm 3 .…”

“…It corresponds to the frequency region ν > 10 10 Hz on the frequency dependences ε 22 (ν) in figure 3. ; [9]; [10]; [14]; [15]. An increase of the relaxation time τ y 2 and a decrease of the relaxation frequency ν y s at approaching the temperature T = T c manifests itself in the shift of the region of dispersion to lower frequencies in the frequency dependence ε 22 (ν) (figure 3) at approaching the temperature T = T c , as well as in the availability of depression near T = T c on the temperature dependence ε 22 (T), and of a sharp peak on the curve ε 22 (T) (figures 4, 5).…”

“…The aim of this paper is to study the relaxation phenomena in GPI and explain the available experimental data [8][9][10][11] for longitudinal dynamic characteristics within the proton ordering model proposed in [5].…”