Synergetic boost of functional properties near critical end points in antiferroelectric systems

The increase of the dielectric permittivity with an electric field and enhanced energy storage properties make antiferroelectrics very attractive for high-power electronic applications needed in emerging green energy technologies and neuromorphic computing platforms. Their exceptional functional properties are closely related to the electric field-induced antiferroelectric\ensuremath{\leftrightarrow}ferroelectric phase transition, which can be driven toward a critical end point by manipulation with an external electric field. The critical fluctuation of physical properties at the critical end point in ferroelectrics is a promising approach to improve their functional properties. Here, we demonstrate the existence of two critical end points in antiferroelectric ceramics with a ferroelectric-antiferroelectric-paraelectric phase sequence, using the model system ${\mathrm{Pb}}_{0.99}{\mathrm{Nb}}_{0.02}{[{({\mathrm{Zr}}_{0.57}{\mathrm{Sn}}_{0.43})}_{0.92}{\mathrm{Ti}}_{0.08}]}_{0.98}{\mathrm{O}}_{3}$. The critical fluctuation of the dielectric permittivity in the proximity of the antiferroelectric-to-paraelectric critical end point is responsible for the strong enhancement of the dielectric tunability (by a factor of $>2$) measured at $\ensuremath{\approx}395$ K. The enhancement of the energy storage density at $\ensuremath{\approx}370$ K is related to the proximity of the ferroelectric-to-antiferroelectric critical end point. These findings open possibilities for material design and pave the way for the next generation of high-energy storage materials.