Conduction mechanism investigation in YCaCuO colossal permittivity ceramics

• Investigated conduction mechanisms in dielectric YCa 2 Cu 3 O δ perovskite. • XRD and XPS characterized the crystal structure of YCa 2 Cu 3 O δ . • Observed paramagnetic insulator-metallic transition in YCa 2 Cu 3 O δ . • Ceramic YCa 2 Cu 3 O δ shows potential for electronic and energy storage. Sol-gel synthesized Y Ca 2 Cu 3 O δ ceramic exhibits giant permittivity ε r ′ ≈ 10 4 , low loss tan δ 0.3 , and high stability over frequency and temperature. XRD revealed a tetragonal phase ( P4/mmm ). XPS confirmed high oxygen vacancy density. The structural heterogeneity, shown by SEM, between neighboring grains results from Schottky barrier formation at the grain boundaries, potentially explaining the TCR phenomenon. Magnetic analysis showed paramagnetism. Electrical property investigation revealed an insulating-to-metallic phase transition with temperature, associated with changing conduction mechanisms. Paramagnetic-insulating behavior at higher temperatures is linked to thermal activation, while electron scattering contributes to paramagnetic-metallic conduction at lower temperatures. The resistivity behavior follows the percolation model, providing insights into the interplay between conducting and insulating phases, relevant for optimizing perovskite-based materials in electronics and energy storage.