Millimetre‐wave investigation of the soft mode in ferroelectric PbHPO₄

Abstract

Abstract, The complex dielectric function C(w) along the a axis of PbHPO, single crystals is determined from reflection measurements at frequencies between 70 and 225 GHz in the paraelectric and the ferroelectric phase near the transition temperature T,. = 310 K. The data are complemented by a remeasurement of the properties of the lowest far-infrared mode. The mm-wave data can be described by a simple Debye formula. The relaxation time exhibits critical slowing down, and the corresponding relaxation frequency varies between about 2 and 60 GHz near T,. Proton tunneling appears to play no essential role in this dielectric mechanism related to proton ordering.

Thermodynamic and dynamic dielectric properties of one-dimensional hydrogen bonded ferroelectric of PbHPO_{4}-type

“…Figures 5 and 6 present the results of calculations of frequency dependencies ε ′ 11 (ν) and ε ′′ 11 (ν), respectively, for LHP as well as experimental data. In these figures it is seen that there is a significant data scattering obtained in the experimental papers [5,32,[34][35][36][37]. The best agreement for our calculated data of ε ′ 11 (ν) and ε ′′ 11 (ν) and the experiment was reached with the results published in papers [5,32,34].…”

“…As seen in this figure, there is quite acceptable agreement between our theoretical results and the majority of experimental data. A significant disagreement is observed only with the experimental data of Briskot et al [34]. The reason is a rather poor experimental accuracy (order of 40-50 %) of their experimental setup.…”

“…In these figures it is seen that there is a significant data scattering obtained in the experimental papers [5,32,[34][35][36][37]. The best agreement for our calculated data of ε ′ 11 (ν) and ε ′′ 11 (ν) and the experiment was reached with the results published in papers [5,32,34]. Figure 7 presents temperature dependencies of real ε ′ 11 (ν, T ) and imaginary ε ′′ 11 (ν, T ) parts of dynamic dielectric permittivity at different frequencies of LHP crystal as well as the experimental data.…”

“…The measured temperature dependencies of a real and imaginary parts of dielectric permittivity at different frequencies for LHP are presented in papers [5,32,[34][35][36][37][38]. In these figures it is seen that there is a significant data scattering obtained in the experimental papers [5,32,[34][35][36][37].…”

“…The measured temperature dependencies of a real and imaginary parts of dielectric permittivity at different frequencies for LHP are presented in papers [5,32,[34][35][36][37][38].…”