Electromechanical dopant-defect interaction in acceptor-doped ceria

Oxygen defective cerium oxides exhibits a non classical giant electromechanical response that is superior to lead based electrostrictors. In this work, we report the key role of acceptor dopants, with different size and valence Mg2+, Sc3+, Gd3+, and La3+, on polycrystalline bulk ceria. Different dopants tune the electrostrictive properties by changing the electrosteric dopant defect interactions. We find two distinct electromechanical behaviors when the interaction is weak dopant vacancy binding energy 0.3 eV, electrostriction displays high coefficient, up to 10-17 m2V-2, with strongly time dependent effects. In contrast, we observe no time dependent effects when the interaction becomes strong 0.6 eV

Assessment of High-Temperature Oxidation Properties of 316L Stainless Steel Powder and Sintered Porous Supports for Potential Solid Oxide Cells Applications

In this work, the oxidation properties of austenitic 316L stainless steel powder and sintered porous support were investigated at the temperature range of ~600–750 °C for 100 hours in ambient air. Oxidation kinetics was deter-mined by continuous thermogravimetry and analyzed employing parabolic rate law. It was observed that oxidation leads to the formation of an oxide scale, with substantial oxidation occurring at ≥ 650 °C in the powder. The porous steel support was fabricated using the tape casting method with two distinct pore former concentrations. The micro-structural features of both the powder and support were investigated by X-ray diffractometry and scanning electron microscopy coupled with energy-dispersive X-ray analysis. The mechanical properties of the metal support were examined before and after oxidation via a microhardness test. The effect of porosity on the resulting properties of the metal support was also highlighted. In summary, 316L stainless steel support suits SOCs applications below 600 °C.</p

Enhanced Mechanical and Electromechanical Properties of Compositionally Complex Zirconia Zr_1-<i>x</i>(Gd_1/5Pr_1/5Nd_1/5Sm_1/5Y_1/5)_<i>x</i>O_2-δ Ceramics

Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition Zr1-x(Gd1/5Pr1/5Nd1/5Sm1/5Y1/5)xO2-δ (x = 0.1 and 0.2) synthesized in solid-state reaction route and sintered via hot pressing at 1350 °C. We explore the evolution of these oxides' structural, microstructural, mechanical, electrical, and electromechanical properties regarding phase separation and sintering mechanisms. Highly dense ceramics are achieved by bimodal mass diffusion, composing nanometric tetragonal and micrometric cubic grains microstructure. The material exhibits an anomalously large electrostriction response exceeding the M33 value of 10-17 m2/V2 at room temperature and viscoelastic properties of primary creep in nanoindentation measurement under fast loading. These findings are strikingly similar to those reported for doped ceria and bismuth oxide derivates, highlighting the presence of a large concentration of point defects linked to structural distortion and anelastic behavior, which are characteristics of nonclassical ionic electrostrictors

Non-classical electrostriction in calcium-doped cerium oxide ceramics

Oxygen-defective metal oxides, e.g., acceptor-doped CeO2, demonstrate exceptionally large electrostrictive responses compared to state-of-the-art electromechanically active ceramic materials. Recent investigations focus on trivalent acceptor (A3+) doped ceria and surmise that giant electrostriction on these compounds depends on the electroactive polarizable elastic dipoles associated with electronic defects in the lattice, e.g., oxygen vacancies V¨ο and polarons. Similarly, to relaxor piezoelectrics, electromechanical responses in doped-ceria strictly depend on the applied field frequency, i.e., time-dependent, revealing a complex interplay between the electro-chemo-mechanic effect in the materials and a loss of properties above 1–10 Hz. This work demonstrates the electromechanical properties of divalent (A2+) calcium-doped ceria (CDC) polycrystalline ceramics with various doping levels (Ce1−xCaxO2−x, x = 0.025–0.15). All the CDC compounds illustrate a steady and high electrostrictive strain coefficient (M33) value exceeding 10−18 m2 V−2 across frequencies between 10−1 and 103 Hz. Notably, the M33 is slightly influenced by the nominal oxygen vacancy concentration, CaO segregation, and the microstructure. These key findings unveil a new form of electromechanical effects in calcium-doped ceria that are rigorously stimulated by the strong electro-steric interaction of Ca2+ — V¨ο pairs

Enhanced Mechanical and Electromechanical Properties of Compositionally Complex Zirconia Zr_1–<i>x</i>(Gd_1/5Pr_1/5Nd_1/5Sm_1/5Y_1/5)<i>_x</i>O_2−δ Ceramics

Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition Zr1–x(Gd1/5Pr1/5Nd1/5Sm1/5Y1/5)xO2−δ (x = 0.1 and 0.2) synthesized in solid-state reaction route and sintered via hot pressing at 1350 °C. We explore the evolution of these oxides’ structural, microstructural, mechanical, electrical, and electromechanical properties regarding phase separation and sintering mechanisms. Highly dense ceramics are achieved by bimodal mass diffusion, composing nanometric tetragonal and micrometric cubic grains microstructure. The material exhibits an anomalously large electrostriction response exceeding the M33 value of 10–17 m2/V2 at room temperature and viscoelastic properties of primary creep in nanoindentation measurement under fast loading. These findings are strikingly similar to those reported for doped ceria and bismuth oxide derivates, highlighting the presence of a large concentration of point defects linked to structural distortion and anelastic behavior, which are characteristics of nonclassical ionic electrostrictors

Oxygen-defective electrostrictors for soft electromechanics

Electromechanical metal oxides, such as piezoceramics, are often incompatible with soft polymers due to their crystallinity requirements, leading to high processing temperatures. This study explores the potential of ceria-based thin films as electromechanical actuators for flexible electronics. Oxygen-deficient fluorites, like cerium oxide, are centrosymmetric nonpiezoelectric crystalline metal oxides that demonstrate giant electrostriction. These films, deposited at low temperatures, integrate seamlessly with various soft substrates like polyimide and PET. Ceria thin films exhibit remarkable electrostriction (M33 &gt; 10−16 m2 V−2) and inverse pseudo-piezo coefficients (e33 &gt; 500 pmV−1), enabling large displacements in soft electromechanical systems. Our study explores resonant and off-resonant configurations in the low-frequency regime (&lt;1 kHz), demonstrating versatility for three-dimensional and transparent electronics. This work advances the understanding of oxygen-defective metal oxide electromechanical properties and paves the way for developing versatile and efficient electromechanical systems for applications in biomedical devices, optical devices, and beyond.</div