High Temperature Impedance Spectroscopic Insights into Modulus and Conductivity Behavior of Bi ₂ O ₃ ‐Doped Ba _0.85 Ca _0.15 Zr _0.1 Ti _0.9 O ₃ Ceramic

In this work, lead‐free (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 (BCZT) ceramic was doped with varying molar percentages of Bi 2 O 3 using a modified solid‐state synthesis method to investigate its high‐temperature impedance, modulus, and conduction properties. Temperature‐dependent Nyquist plots of Z″ versus Z′ showed two semicircles, attributed to grains and grain boundaries and its’ relative radii and capacitances changed systematically with Bi content. Additionally, the negative temperature coefficient resistance (NTCR) behavior of all materials was confirmed by the decrease in radii values with temperature increments. Impedance and modulus analysis further indicated that specific B‐site doped BCZT‐04Bi sample showed relatively uniform defect landscape, reducing activation energy and narrowing the relaxation distribution, whereas higher Bi‐doped BCZT‐07Bi sample lead to mixed A/B‐site incorporation, resulted into nonuniform relaxation which is artributed to the larger grain/grain‐boundary capacitances, and increased activation energy. The hopping‐dominated conduction mechanism and the interrelation between AC and DC conductivity were established by Almond and West (AW), as well as Barton, Nakajima, and Namikawa (BNN) analyses. Conductivity scaling (time–temperature superposition principle (TTSP)) behavior demonstrated the most scalable charge dynamics for BCZT‐04Bi. Thermal sensitivity indices β exceed 3000 K, confirming the strong NTC thermistor performance in the temperature range of 320–420°C for all the prepared samples. Notably, BCZT‐07Bi reached the highest β ‐value of 4771 K.