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Abstract Lead‐free piezoceramics with the composition (1−x) (K 1− y N a y) NbO 3 ‐x (Bi 1/2 Na 1/2) ZrO 3 (KN yN‐ 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 (P r =24 μC/cm 2), piezoelectric coefficient (d 33 =320 pC /N), effective piezocoefficient (d₃₃^*=420 pm/V), coupling coefficient (k p =48%), and high strain (S =0. 168%) were obtained at room temperature, but significant deterioration of P r, d₃₃^*, and k p were observed by increasing from room temperature to 160°C (17. 5 μC/cm 2, 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.
Wang et al. (Tue,) studied this question.