(1–x)K_0.5Na_0.5NbO₃-xLaBiO₃ [(1–x)KNN-xLB, x = 0, 0.005, 0.015] lead-free ceramics were prepared via a solid-state reaction route. An orthorhombic symmetry was determined for all samples by the Rietveld refinement of XRD patterns. The 0.995KNN-0.005LB ceramic (KNN-5LB) exhibits an ultrahigh and stable relative permittivity (ε’ ~ 2158 ± 15%) with a low dielectric loss tangent (tanδ ≤ 3%) in a very broad operation temperature range from 172 °C to 450 °C due to two close diffuse phase transitions at ~200 °C and ~ 380 °C induced by La and an additional polarization from off-centered Bi ions. The Cole-Cole plot of iso-thermal complex impedance suggests that the high-temperature dielectric response of the KNN-5LB is attributed to the polarizations from grains, grain boundaries and electrode interfaces. Both the imaginary parts of impedance and modulus exhibit the thermally activated process and scaling behavior. The frequency dependent conductivity (σ_ac) of the KNN-5LB follows the Universal Dielectric Response (UDR) law. The conduction mechanism is related to the small polaron hopping.

(1– x )K _0.5 Na _0.5 NbO ₃ - x LaBiO ₃ [(1– x )KNN- x LB, x  = 0, 0.005, 0.015] 无铅陶瓷是通过固态反应路线制备的。通过 XRD 图案的 Rietveld 精修确定所有样品的正交对称性。0.995KNN-0.005LB 陶瓷 (KNN-5LB) 具有超高且稳定的相对介电常数 ( ε'  ~ 2158 ± 15%) 和低介电损耗角正切 (tan δ ≤ 3%) 在从 172 °C 到 450 °C 的非常广泛的操作温度范围内，由于 La 引起的 ~200 °C 和 ~ 380 °C 两个紧密的扩散相变以及偏心 Bi 离子的额外极化。等温复阻抗的 Cole-Cole 图表明 KNN-5LB 的高温介电响应归因于晶粒、晶界和电极界面的极化。阻抗和模量的虚部都表现出热激活过程和缩放行为。KNN-5LB的频率相关电导率 ( σ _ac ) 遵循通用介电响应 (UDR) 定律。传导机制与小极化子跳跃有关。