Dopant concentration controls quasi-static electrostrictive strain response of ceria ceramics

Electromechanically active ceramic materials, piezoelectrics and electrostrictors, provide the backbone of a variety of consumer technologies. Gd- and Sm- doped ceria are ion conducting ceramics, finding application in fuel cells, oxygen sensors and, potentially, as memristor materials. While optimal design of ceria-based devices requires thorough understanding of their mechanical and electro-mechanical properties, reports of systematic study of the effect of dopant concentration on the electromechanical behavior of ceria-based ceramics are lacking. Here we report the longitudinal electrostriction strain coefficient (M33) of dense RExCe(1-x)O(2-x/2) (x≤0.25) ceramic pellets , where RE=Gd or Sm, measured under ambient conditions as a function of dopant concentration within the frequency range f=0.15-350 Hz, electric field amplitude E≤0.5 MV/m. For >100 Hz , all ceramic pellets tested, independent of dopant concentration, exhibit longitudinal electrostriction strain coefficient with magnitude on the order of 10-18 m2/V2. The quasi-static (f<1 Hz ) electrostriction strain coefficient for undoped ceria is comparable in magnitude, while introducing 5mol% Gd or 5mol% Sm produces an increase in M33 by up to two orders of magnitude. For x≤0.1 (Gd)- 0.15 (Sm), the Debye-type relaxation time constant (τ) is in the range 60-300 msec. The inverse relationship between dopant concentration and quasi-static electrostrictive strain parallels the anelasticity and ionic conductivity of Gd and Sm-doped ceria ceramics, indicating that electrostriction is partially governed by ordering of vacancies and changes in local symmetry.