Theoretical investigation of ferroelectric and dielectric properties of Rochelle salt colemanite type crystals

Studies of Rochelle salt crystals such as colemanite (Ca2B6O11.5H(2)O), which exhibits ferroelectricity below -7 degrees C, are performed using a modified two-sublattice pseudospin model Hamiltonian. This Hamiltonian model includes terms for phonon anharmonic interactions up to the fourth order. Using this and the dual thermal Green's function, formulations for ferroelectric mode frequencies, permittivity, and loss tangent for colemanite crystals were derived. The model values were fitted to the derivation to obtain the above quantities of thermal variation. The theoretical variations in these quantities were compared with the experimental variations reported by Gavrilova et al. reported to be in good agreement.