Critical exponents of the order parameter of diffuse ferroelectric phase transitions in the solid solutions based on lead germanate: studies of optical rotation

• Main Authors: Adamenko, D. I, Vlokh, R. O
• Format: Journal Article
• Language: English
• Published: 03-01-2023
• Subjects: Physics - Materials Science; Physics - Other Condensed Matter
• DOI: 10.48550/arxiv.2301.01346

Condensed Matter Physics, 2022, vol. 25, No. 4, 43703 In this work we show that the critical exponents of the order parameter
(CEOPs) of diffuse ferroelectric phase transitions (DFEPTs) occurring in lead
germanate-based crystals can be determined using experimental temperature
dependences of their optical rotation. We also describe the approach that
suggests dividing a crystal sample into many homogeneous unit cells, each of
which is characterized by a non-diffuse phase transition with a specific local
Curie temperature. Using this approach, the CEOPs have been determined for the
pure Pb$_{5}$Ge$_{3}$O$_{11}$ crystals, the solid solutions
Pb$_{5}$(Ge$_{1-x}$Si$_{x}$)$_{3}$O$_{11}$ ($x = $0.03, 0.05, 0.10, 0.20, 0.40)
and (Pb$_{1-x}$Ba$_{x}$)$_{5}$Ge$_{3}$O$_{11}$ ($x =$ 0.02, 0.05), and the
doped crystals Pb$_{5}$Ge$_{3}$O$_{11}$:Li$^{3+}$ (0.005 wt. %),
Pb$_{5}$Ge$_{3}$O$_{11}$:La$^{3+}$ (0.02 wt. %),
Pb$_{5}$Ge$_{3}$O$_{11}$:Eu$^{3+}$ (0.021 wt. %),
Pb$_{5}$Ge$_{3}$O$_{11}$:Li$^{3+}$, Bi$^{3+}$ (0.152 wt.~\%) and
Pb$_{5}$Ge$_{3}$O$_{11}$:Cu$^{2+}$ (0.14 wt. %). Comparison of our approach
with the other techniques used for determining the Curie temperatures and the
CEOPs of DFEPTs testifies to its essential advantages.