Investigation of phase transition behaviour in antiferroelectric squaric acid crystal

In this paper, we investigated the temperature dependence of the dielectric properties of the antiferroelectric phase transition in a squaric acid crystal. Several equations for the soft mode frequency, dielectric constant, and loss tangent were derived using the modified two-sublattice pseudospin lattice couple mode model Hamiltonian and the Green function approach. The temperature dependence of the soft mode frequency, dielectric constant, and loss tangent of the antiferroelectric squaric acid crystal was derived from the various fitted values of the different physical parameters to the derived equations. The theoretical results compared well with the experimental results; likewise, based on the literature, squaric acid has shown different complex behaviours of antiferroelectric properties while functionally serving many purposes, including medical, electronics, and optics. The soft mode behaviour shows evidence of a second-order phase transition, which translates to an order–disorder mechanism for antiferroelectric squaric acid. The evaluation of the dielectric response and loss tangent assesses the integrity/stability of a material while exposed to various thermal conditions and is important for its usefulness in potential applications.