B-site ion driven morphotropic phase transformation in NN-BT-ABO3 lead-free ceramics through chemical pressure

作者：Tian, Ao; Fu, Jian^*; Yu, Zide; Zuo, Ruzhong^*

来源：Journal of Alloys and Compounds, 2023, 960: 170776.

DOI：10.1016/j.jallcom.2023.170776

• NaNbO3-based
• Piezoelectric ceramic
• Morphotropic phase boundary
• Lead-free
• Phase transformation

Forming morphotropic phase boundary (MPB) is crucial to improve the piezoelectric properties of lead-free NaNbO3-BaTiO3-xABO3 (NN-BT-xABO3) ceramics. In this work, four NN-BT-xABO3 systems (ABO3 = K0.5Bi0.5TiO3 (KBT), Bi0.5Na0.5TiO3 (BNT), K0.5Bi0.5ZrO3 (KBZ), and Bi0.5Na0.5ZrO3 (BNZ)) were constructed to analyze the relationship between ABO3 characteristic and phase transformation behavior. The results showed that the NN-BT-xKBT/xBNT systems underwent ferroelectric tetragonal (T)-relaxor ferroelectric T phase transformation with d33 & SIM; 150 pC/N and kp & SIM; 0.2 in NN-BT-0.11KBT and NN-BT-0.09BNT compositions, while the NN-BT-xKBZ/ xBNZ systems underwent ferroelectric T-ferroelectric rhombohedral (R) morphotropic phase transformation with improved d33 & SIM; 256 pC/N and kp & SIM; 0.31 in NN-BT-0.04BNZ composition. The B-site ion radius was found to be a key factor in inducing phase transformation. The incorporation of small Ti4+ ions tends to break the long ordering of ferroelectrics, inducing the normal-relaxor ferroelectric phase transformation, however, the ap-pearance of the R phase in NN-BT-xAZrO3 compositions was attributed to the chemical pressure caused by buckled Zr-O-Zr bonds as larger Zr4+ ions enter the NN-BT matrix lattices. This study will deepen the un-derstanding of the ferroelectric phase transformation mechanism in the lead-free NaNbO3 material system and provide a guidance for designing morphotropic NN-based lead-free piezoelectric ceramics.& COPY; 2023 Elsevier B.V.