Dielectric Permittivity of Nonstoichiometric Lead Germanate Crystals

Analysis of Theoretical Models for Nonlinear Fitting of Experimental Data: Dielectric Permittivity of Pb4.95Ge3O11 Crystals

“…Due to many influencing effects, a standard linear fitting is no good here. It must be replaced by much more cumbersome techniques of nonlinear fitting (see, e.g., [6,7]), of which performance and efficiency represent a separate subject.…”

Nonlinear background corrections to dielectric permittivity of ferroics and multiferroics

“…According to the PbO and GeO 2 contents in charge, nonstoichiometric PGO can be described using a conditional formula Pb 4.95 Ge 3 O 11 . This PGO compound represents a ferroelectric with a second-order PT at the Curie point 𝑇 C ≈ 435 K (the symmetry 𝑃6 ↔ 𝑃3), in which Pb vacancies of a preset concentration were created [21,28]. Strong dipole-dipole correlations must have been available in this uniaxial ferroelectric.…”

“…Figure 1 shows the temperature dependence of the dielectric permittivity for the PGO crystals. The nonstoichiometry broadens and drastically suppresses the anomaly at the PT (see also [21,28]). Nonetheless, diffuseness of the PT is not clearly seen.…”

Temperature dependence of dielectric permittivity in incommensurately modulated phase of ammonium fluoroberyllate

“…Such a small 𝜀 max peak can indeed be successfully interpreted using the idea that the dielectric anomaly in improper ferroelectrics is a secondary effect while a true order parameter has the symmetry different from that of spontaneous electric polarization. For the same or somewhat different reasons, weak dielectric anomalies are also typical of ferroelastics [20], multiferroics [21] and ferroelectrics with noticeable amounts of structural defects [14,15,22]. Now we proceed to phenomenological consideration of the dielectric properties of AFB.…”

“…The other notable fact is that there has been no study where an experimental temperature dependence of the dielectric permittivity for the AFB crystals would be simultaneously compared with different theoretical formulae in order to estimate the advantages and shortcomings of the latter. The only exception, our recent work [13], represents a short technical report based upon contemporary methods of nonlinear fitting and statistical techniques (see the works [14,15]). Although a number of weak methodical points associated with fitting [16][17][18] are omitted in this work, no physical reasoning and data interpretation have been made there.…”