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

D. I. Adamenko; R. O. Vlokh

doi:10.5488/CMP.25.43703

paper

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

arXiv:2301.01346 · doi:10.5488/CMP.25.43703

Abstract

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.

9 pages, 6 figures, 3 tables