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We present a thermodynamic analysis of the recently discovered nitride ferroelectric materials using the classic Landau–Devonshire approach. Electrostrictive and dielectric stiffness coefficients of Al1−xScxN with a wurtzite structure (6 mm) are determined using a free energy density function assuming a hexagonal parent phase (6/mmm), with the first-order phase transition based on the dielectric stiffness relationships. The results of this analysis show that the strain sensitivity of the energy barrier is one order of magnitude larger than that of the spontaneous polarization in these wurtzite ferroelectrics, yet both are less sensitive to strain compared to classic perovskite ferroelectrics. These analysis results reported here explain experimentally reported sensitivity of the coercive field to elastic strain/stress in Al1−xScxN films and would enable further thermodynamic analysis via phase field simulation and related methods. [ABSTRACT FROM AUTHOR]

With the urgent need to explore low‐cost, high‐efficiency solid‐state refrigeration technology, the electrocaloric effects of ferroelectric materials have attracted much attention in the past decades. With the development of modern computing technology, the phase‐field method is widely used to simulate the evolution of microstructure at mesoscale and predict the properties of different types of ferroelectric materials. In this article, we review the recent progress of electrocaloric effects from phenomenological Landau thermodynamics theory to phase‐field simulation by discussing the microcosmic composition, mesoscopic domain structures, macroscopic size/shape, and external stimulus of strain/stress. More importantly, in searching for new ferroelectric electrocaloric cooling materials, it is possible to find materials whose free energy barrier height changes rapidly with temperature, such materials have a faster change rate with polarization temperature in terms of ferroelectric macroscopic properties, from them could get superior electrocaloric effects. We compile a relatively comprehensive computational design on the high performance of electrocaloric effects in different types of ferroelectrics and offer a perspective on the computational design of electrocaloric refrigeration materials at the mesoscale microstructure level. [ABSTRACT FROM AUTHOR]

Based on the Devonshire theory, the E-induced effects of polarization, dielectrics, hysteresis loop, and energy storage are investigated. Numerical simulations confirm that the ferroelectrics with soft ferroelectricity with properties of small and E-sensitive polarization, abrupt decrease of dielectric peak with increasing E, sloped and slender hysteresis loop with central narrow when approaching Tc, and symmetry energy storage peak, much less than Tc, towards high temperature with increasing E, can be the candidate of high energy storage materials. E-induced polarization effect is related with thermodynamic parameters of ferroelectrics. Peak of energy storage shifts to high temperature under high-E. Larger induced polarization is corresponding to higher energy storage. [ABSTRACT FROM AUTHOR]