Modulation on structure and electric properties by tantalum of lead-free NaNbO3 ceramics

The variation of structural and electric properties is investigated via different characterization methods for NaNbO₃ ceramics modified with Ta⁵⁺ ions. At room temperature, substitution of Ta⁵⁺ ions can effectively induce the phase coexistence and transition between orthorhombic antiferroelectric P and orthorhombic ferroelectric Q phase in NaNb_1-xTa_xO₃ ceramics. Thus, the ferroelectric and piezoelectric properties could be regulated with the maximum value of d₃₃ (~37.3) at x = 0.05. Besides, with increasing temperature, multiple phase transitions are demonstrated through dielectric, XRD, and in situ Raman results. Moreover, the temperature of various phase transitions gradually shifts toward lower temperature with increasing Ta⁵⁺ ions. Correspondingly, the modulation mechanism is also discussed based on the evolution of Raman vibration. This work is instructive for regulatable applications of NaNbO₃-based materials.