Understanding Crystal Spatial Symmetry of Sm/Mg Heterovalent‐Doped BST–BNT Ceramics: An Effect Mechanism for Electrical Properties

The effect mechanism of lattice distortion caused by heterovalent rare‐earth and alkaline‐earth ions co‐doping in the electrical properties of piezo‐ceramics is generally concerning. Herein, the Sm2O3/MgO co‐doped 0.65(Ba0.96Sr0.04TiO3)–0.35(Bi0.50Na0.50TiO3) (BST–BNT: x(Sm, Mg)) (0 ≤ x ≤ 0.25 wt%) ceramics are prepared by Pechini sol–gel method. The reversibility transition from the tetragonal P4/mmm relaxation paraelectric phase to the tetragonal P4mm relaxation ferroelectric phase confirms the doping‐modulated piezoelectric constants’ response to the spatial symmetry. Excessive Sm3+ and Mg2+ in the interstitial lattice inhibit the Jahn–Teller effect of distortion in the crystal spatial symmetry. The restored P4/mmm spatial symmetry of BST–BNT: x(Sm, Mg) (x = 0.15 wt%) ceramics contributes to the large electric‐induced strain, increased Curie temperature, and the stabilized frequency dependence of the Curie temperature (TC [1 MHz] = 167 °C, εr [1 MHz] = 2151.92, d33 = 43 pC N−1, Smax/Emax = 535.22 pm V−1). The samples with large electric‐induced strain and good temperature stability of electrical properties can be applied in the heat dissipation actuators.