A phenomenological gibbs function for BaTiO3 giving correct e field dependence of all ferroelectric phase changes

The elastic Gibbs function for BaTiO3 introduced by Buessem, Goswami and Cross1 has been modified by including the last symmetry permitted sixth order term HP12P22P32 with a coefficient H = 4.91 × 109 Vm9 C-5. The function predicts the correct high electric field behavior of the low temperature ferroelectric: ferroelectric phase changes in the single crystal and suggests an interesting change of sign of the pyroelectric effect at high field levels in the induced tetragonal ferroelectric phase.