Composition and temperature dependence of structure and piezoelectricity in (1−x)(K1−yNay)NbO3‐x(Bi1/2Na1/2)ZrO3 lead‐free ceramics

• Published in: Journal of the American Ceramic Society 2017-02, Vol.100 (2), p.627-637
• Main Authors: Wang, Dawei, Hussain, Fayaz, Khesro, Amir, Feteira, Antonio, Tian, Ye, Zhao, Quanliang, Reaney, Ian M.
• Format: Article
• Language: English
• Subjects: Ceramics; Dielectric properties; Diffraction; lead‐free ceramics; piezoelectric materials/properties; potassium‐sodium niobate/KNN; Spectrum analysis
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.14589

Lead‐free piezoceramics with the composition (1−x)(K1−yNay)NbO3‐x(Bi1/2Na1/2)ZrO3 (KNyN‐xBNZ) were prepared using a conventional solid‐state route. X‐ray diffraction, Raman spectroscopy, and dielectric measurements as a function of temperature indicated the coexistence of rhombohedral (R) and tetragonal (T) phase, typical of a morphotropic phase boundary (MPB) as the BNZ concentration increased and by adjusting the K/Na ratio. High remnant polarization (Pr=24 μC/cm2), piezoelectric coefficient (d33=320 pC/N), effective piezocoefficient ({d_{33}^*}=420 pm/V), coupling coefficient (kp=48%), and high strain (S=0.168%) were obtained at room temperature, but significant deterioration of Pr, {d_{33}^*}, and kp were observed by increasing from room temperature to 160°C (17.5 μC/cm2, 338 pm/V, and 32%, respectively) associated with a transition to a purely T phase. Despite these compositions showing promise for room‐temperature applications, the deterioration in properties as a function of increasing temperature poses challenges for device design and remains to be resolved.