Structure, ferroelectric, and dielectric properties of (Na1−2xCax)NbO3 ceramics

Mimicking the scheme of incorporating La3+ to Pb(Zr1−xTix)O3, Ca2+ is used to substitute Na+ in the lead-free NaNbO3 compound, with A-site vacancy introduced to maintain charge neutrality. The anticipated relaxor behavior is expected to suppress the remanent polarization and improve the energy storage properties of NaNbO3-based ceramics. Specifically, (Na1−2xCax)NbO3 (x = 0.01, 0.02, 0.04, 0.08) ceramics were prepared with the solid-state method, and their structures and electric properties were investigated. X-ray diffraction and transmission electron microscopy reveal the existence of minor amount of CaNb2O6 second phase. Polarization vs. electric field hysteresis loop measurements verify the suppression of remanent polarization in compositions of x ≤ 0.04. The temperature-dependent dielectric tests indicate that both the relaxation and diffuseness parameters monotonically increase with Ca2+ content. The results demonstrate that the introduction of a smaller donor dopant and charge-compensating vacancies on the A-site in NaNbO3 is an effective strategy to disrupt the long-range dipole order.

模仿将La³⁺掺入Pb(Zr₁₋ₓTiₓ)O₃的方案，在无铅NaNbO₃化合物中使用Ca²⁺替代Na⁺，并引入A位空位以保持电荷中性。预期的弛豫特性有望抑制剩余极化并改善NaNbO₃基陶瓷的储能性能。具体而言，采用固相法制备了(Na₁₋₂ₓCaₓ)NbO₃（x = 0.01、0.02、0.04、0.08）陶瓷，并对其结构和电学性能进行了研究。X射线衍射和透射电子显微镜显示存在少量CaNb₂O₆第二相。极化 - 电场滞回曲线测量证实，在x ≤ 0.04的成分中剩余极化得到抑制。温度相关的介电测试表明，弛豫参数和弥散参数都随Ca²⁺含量单调增加。结果表明，在NaNbO₃的A位引入较小的施主掺杂剂和电荷补偿空位是破坏长程偶极有序的有效策略。