Simultaneously enhanced electrical properties and high-power characteristics of (K,Na)NbO3 lead-free piezoceramics by hot-pressing

Abstract

Piezoelectric materials enabling direct conversion between electrical and mechanical energies are ubiquitously implemented in high-power apparatuses, where both superior piezoelectricity and high-power performance are demanded. However, it remains a challenge to simultaneously achieve the two goals, which are hindered by their antagonistic relationship. Herein, hot-pressing is employed to address this dilemma, as exemplified in lead-free (K,Na)NbO3 (KNN) piezoceramics. In contrast to the samples prepared using normal sintering (NS–KNN), hot-pressed KNN (HP–KNN) polycrystals show higher density, lager piezoelectricity (d33∼129 pC/N), and more active domain wall movement. In particular, the normalized strain d33* of HP-KNN piezoceramics exhibits high thermal stability (variation of d33*<10 %) in a broad temperature range from ambient temperature up to 150 °C. Moreover, the HP-KNN samples show superior high-power characteristics with a maximum vibration speed of 1.1 m/s, which is almost 78 % larger than that of NS-KNN. This study not only demonstrates that the HP-KNN lead-free piezoceramics hold great potential for high-power implements, but also opens a new avenue for integrating antagonistic properties for the enhancement of the collective performance in functional materials.