5. Conclusions

One-dimensional models that reflect the hysteretic properties of polycrystalline ferroelectric media on the external effects of high-intensity electric and mechanical fields are considered. The bases of construction of each model are disassembled. The fundamentals of the construction of each of the well-known Rayleigh models, evolution models, models of plasticity theory, Preisach models, models of orientation switching, energy switching models, the Giles-Atherton model are analyzed and the results of their work in the form of hysteresis loops are presented. The main advantages and disadvantages of each model are noted; in particular, the differential and integral properties of hysteresis dependences are marked. It is noted that each of the models has a number of parameters, the choice of which affects the shape of the hysteresis loop. However, in the mathematical sense, such a choice generates additional difficulties, which are connected with the solution of inverse problems. Unresolved problems in the general problem of modeling the polarization of polycrystalline ferroelectric materials are noted. A list of works is given in which the main ideas and results of each of the earlier models are reflected.
