Sn4+-modified Ti-rich CaCu3Ti4.5O12 ceramics with low loss and X8R-Grade thermal stability prepared by polymer pyrolysis

Sn 4+ substitution at the Ti sites of CaCu 3 Ti 4.5 O 12 ceramics was successfully achieved via a polymer pyrolysis technique. The effects of Sn 4+ incorporation on the dielectric and nonlinear electrical properties were systematically examined. XRD and FE-SEM analyses confirmed the coexistence of CaCu 3 Ti 4 O 12 and TiO 2 phases with refined grains and uniformly dispersed secondary phases, while EDXS mapping revealed suppressed CuO segregation together with enhanced TiO 2 homogeneity along grain boundaries. Consequently, the CaCu 3 Ti 4.3 Sn 0.2 O 12 ceramic sintered at 1060 °C for 6 h exhibited a high permittivity (ε′ ≈ 7.45 × 10 3 ) and ultralow dielectric loss (tan δ = 0.027 at 1 kHz, 30 °C) , together with excellent temperature stability (Δε′ < ±15% from −60 to 150 °C) , meeting the X8R capacitor standard . Nonlinear J–E analysis revealed a significant enhancement in α (≈ 35.9) and E b (≈ 1.32 × 10 4 V.cm -1 ) , suitable for varistor applications. The improved dielectric and nonlinear responses stemmed from increased grain-boundary resistance ( R gb ≈ 224.1 kΩ.cm) and higher barrier height (Φ B ≈ 1.15 eV), both induced by Sn 4+ substitution and microstructural refinement. XANES results revealed a slight Ti 4+ → Ti 3+ reduction, enhancing small-polaron hopping in semiconducting grains and maintaining strong grain-boundary insulation, which together shape the dielectric and nonlinear behaviors. These synergistic effects enable high stability, low loss, and strong non-Ohmic performance, positioning Sn-doped CaCu 3 Ti 4+ x O 12 ceramics as promising candidates for next-generation capacitor–varistor integration. • Sn 4+ -doped CaCu 3 Ti 4.5 O 12 ceramics were synthesized via a polymer pyrolysis route. • CaCu 3 Ti 4.3 Sn 0.2 O 12 sintered at 1060 °C for 6 h exhibited ε′ = 7.45 × 10 3 and tan δ = 0.027. • Excellent Δε′ < ±15 % (−60–150 °C) satisfies the X8R capacitor requirement. • Enhanced α = 35.9 and E b = 1.32 × 10 4 V.cm -1 enable varistor functionality. • Improved dielectric and nonlinear behavior originated from strong IBLC-type grain boundaries.