Electrostrictive Coefficients of 0.9Pb(Mg 1/3 Nb 2/3 )O ₃ ‐0.1PbTiO ₃ Relaxor Ferroelectric Ceramics in the Ferroelectricity‐Dominated Temperature Range

Polarization and strain induced by unipolar electric fields (P uni , S uni ) as well as those induced by bipolar electric fields (P bi , S bi ) were measured in 0.9Pb(Mg l/3 Nb 2/3 )O 3 ‐0.1PbTiO 3 relaxor ferroelectric ceramics in the temperature range of −50°‐90°C to observe the phase transition in this region and calculate the electrostrictive coefficients from the purely electric‐field‐induced polarization and strain. By considering both the electrostrictive component (F uni , S uni ) and the piezoelectric component ( P r , S r ), it is shown quantitatively how the transition occurs from pure electrostrictive to partially piezoelectric properties across the phase transition range. P uni represents unmixed electric‐field‐induced polarization. while F bi represents the summation of P uni and P r . Similarly, S uni represents unmixed electric‐field‐induced strain, while S bi represents the summation of S uni and S r . The effective electrostrictive coefficient (Q eff ) is calculated even in the ferroelectric region far below the phase transition temperature using S uni and P uni which are purely electric field induced. Q eff significantly increases as the temperature decreases below the phase transition temperature, which was attributed to the decreased rattling space of B‐site atoms.