Effect of cold sintering temperatures on the microstructure and mechanical properties of BaZr0.7Ce0.2Y0.1O3-δ proton conductors

• BZCY721 ceramics were prepared by cold sintering (150–350 °C) and PTT at 1300 °C. • Cold sintering produced fine-grained materials with additional phases/impurities. • Better density and mechanical properties were observed for cold sintered materials. • Mechanical performance depended on undulations regardless of sintering conditions. • Conductivity of cold sintered material was close to the conventionally sintered. Conventional sintering of barium zirconate cerates for proton-conducting ceramic membranes requires high temperatures (1500–––1600 °C) and long dwell times (>24 h), leading to Ba evaporation that negatively impacts conductivity. This study adapted the cold sintering process (CSP) to consolidate BaZr 0.7 Ce 0.2 Y 0.1 O 3-δ (BZCY721) ceramics at 150–––350 °C, followed by post-thermal treatment at 1300 °C. The cold sintered specimens were characterized for mechanical properties and compared to a specimen sintered conventionally at 1600 °C. The cold sintered materials exhibited a Zr-rich BZY phase (BaZr 0.9 Y 0.1 O 2.68 ) with smaller grain and pore sizes. The highest density and elastic modulus were found in the specimen cold sintered at 150 °C. Additionally, the hardness of the cold sintered samples was higher than that of the conventional reference due to finer grain size and reduced porosity. Fracture toughness measurements by the Vickers indentation test indicated a value of 1.26 MPa·m 0.5 for cold sintered specimens, compared to 0.93 MPa·m 0.5 for the conventionally sintered specimen. The specimen cold sintered at 150 °C yielded the highest fracture toughness value of 1.48 MPa·m 0.5 by micro-pillar splitting test, along with the total conductivity of 1.48 × 10 −4 S/cm at 400 °C, which is comparable to the conventionally processed reference.