Ultrafast Densification of Lead‐Free ZnO‐Doped KNN via Flash Sintering

ABSTRACT Flash sintering (FS) is a recently discovered technique of ultrafast densification. In this work, the effect of stoichiometry and ZnO doping on FS of K _0.5 Na _0.5 NbO ₃ (KNN) is studied. A comparison has been made between the dielectric and piezoelectric properties of FS KNN with conventionally sintered KNN. The theoretical density of ∼92% was achieved under an applied electric field of 500 V/cm at the furnace temperature of 900°C in 120 s, which is ∼200°C less than conventional sintering. The dielectric constant of FS KNN for various frequencies at high temperatures is significantly lower (till transition temperature), but with lower dielectric loss. The curie point of the flash‐sintered sample is 30°C higher than the conventionally sintered sample, while the piezoelectric constant is found to be almost the same. The differences in the piezoelectric and dielectric properties of samples sintered via FS and conventional sintering have been assigned to variations in the structure and microstructure because of the electric field.