Effect of the secondary phase content on the ferroelectric, piezoelectric, and dielectric properties of 0.96(K0.48Na0.52)Li0.05Nb0.95Ta0.05O3-0.04BaZrO3 piezoceramics

Lead-free KNN-based piezoceramics with different contents of secondary phase were synthesized via conventional solid-state method. The influence of the tungsten-bronze secondary phase on the ferroelectric, piezoelectric and dielectric properties was systematically investigated. The presence of the secondary phase significantly deteriorated the materials performance, reducing both piezoelectric and ferroelectric response. Specifically, the d 33 increased from 142 pC/N for ceramics containing \:\:~ 1.5 wt% of tungsten-bronze (TB) secondary phase to 203 pC/N for the KNLNT-BZ sample with less than 0.3% of TB phase. Despite the relatively low secondary-phase content (< 2 wt%), the piezoelectric response decreased by near 34%, highlighting the strong sensitivity of KNN-based systems to phase purity. These findings confirm that strict control of secondary phases is essential to maximize the electromechanical performance of lead-free KNN piezoelectric ceramics.