Trivalent Dopant Size Influences Electrostrictive Strain in Ceria Solid Solutions.

Area of Science:

• Materials Science
• Solid State Physics
• Ceramic Engineering

Background:

• Electrostrictors and piezoelectrics are crucial for applications within the tens of Hz to tens of kHz range.
• Ceria ceramics doped with Sm³⁺ and Gd³⁺ show large electrostriction below 1 Hz, but the underlying mechanisms remain unclear.
• Understanding dopant size effects on frequency response is vital for optimizing ceria-based devices.

Purpose of the Study:

• To systematically investigate the influence of trivalent lanthanide dopant size on the mechanical and electromechanical properties of ceria ceramics.
• To explore the frequency-dependent electrostrictive behavior of these doped ceria materials.

Main Methods:

• Ultrasound pulse echo measurements were used to determine Young's, shear, and bulk moduli.
• Nanoindentation was employed to assess room-temperature creep and viscoelastic behavior (anelasticity).
• Electrostriction measurements were conducted across a frequency range of 0.15–150 Hz with electric fields up to 0.7 MV/m.

Main Results:

• All doped ceria samples exhibited viscoelastic behavior, including room-temperature creep.
• Longitudinal electrostriction strain coefficients were significantly higher (10²–10⁴-fold) than classical electrostrictors across the studied frequency range.
• Electrostrictive strain showed frequency relaxation in Er-, Gd-, Sm-, and Nd-doped ceria, but not in Lu- and Yb-doped samples, indicating dopant size dependency.

Conclusions:

• Smaller dopants (Lu, Yb) in ceria ceramics maintain usable electrostrictive strain at higher frequencies compared to larger dopants.
• The observed frequency response differences suggest dopant size dictates the dominant type of induced polarizable elastic dipoles.
• These findings are critical for designing advanced ceria-based electrostrictive devices operating across a wider frequency spectrum.