Strain regulation via composition and valence dependent substitution in BNT-based solid solutions

Abstract

Simultaneous composition and valence-dependent strain regulation is achieved in lead-free (Bi0.5Na0.4K0.1)1-2xSm2xTi1-xMnxO3 (BNKT-SM100x) ceramics by a facile co-doping design with Sm3+ and Mn2+. By simply controlling the sintering temperature, Mn ions exhibited mixed-oxidation states with different ion radius and electronic structures, further adjusting the crystalline field. The regulated disorder degree finally induced large electro-strain (0.445%) under appropriate doping contents (x ​= ​0.01) and sintering temperature (1150 ​°C). Moreover, the random effect of Mn2+ (arising from the different valence and radius comparing with Ti4+) is stronger than the pinning effect due to the suppressed oxygen vacancies, and the different crystal structures may also affect the role of Mn2+. The domain morphologies with mixed nanodomain and ferroelectric domain were observed in the BNKT-SM1 ceramics, further demonstrating the coexistence of random effect and pinning effect. It is believed that the self-strain regulation phenomenon in this work may serve as an effective strategy for designing ferroelectrics with high strain performance.

Keywords

• Lead-free piezoelectric
• BNKT
• Strain regulation
• Mn valence
• Ferroelectric ceramics