Phenomenological Study of Lithium-Sodium Tetragermanate Close to the Phase Transition

Abstract

This study presents an analysis of the dielectric and thermal properties in the vicinity of the second-order ferroelectric phase transition, with a specific emphasis on lithium-sodium tetragermanate, LiNaGe<inf>4</inf>O<inf>9</inf>. The power-law equation is employed by modifying the Kouvel-Fisher (KF) technique, which articulates the magnetization () and magnetic susceptibility in relation to the spontaneous polarization () and the dielectric constant () within ferroelectric frameworks. A parallel methodology is adopted to elucidate the heat capacity () and thermal expansivity () in the vicinity of phase transitions occurring in LiNaGe<inf>4</inf>O<inf>9</inf>. We demonstrate that the continuous fluctuations in and with temperature nearing the Curie point (T<inf>C</inf>108 K) as an indication of a second-order transition in LiNaGe<inf>4</inf>O<inf>9</inf>. Furthermore, a linear correlation is also established between and with temperature approaching the Curie point T<inf>C</inf> for this crystal structure. Experimental data are used from the literature for our analysis. Our findings show that the critical behavior of one dielectric or thermal property near the transition temperature in LiNaGe<inf>4</inf>O<inf>9</inf> can be predicted from the other through these linear relationships. The methodology articulated herein for delineating the dielectric and thermal characteristics of LiNaGe<inf>4</inf>O<inf>9</inf> close to the Curie point is extendable to various other ferroelectric materials. © 2025 Elsevier B.V., All rights reserved.