Optimization of low sintering temperature for colossal permittivity and humidity resistance in TiO₂ based ceramics

This study investigates the colossal permittivity (CP) and humidity resistance of (Sn_1/2Nb_1/2)_0.025Ti_0.975O₂ ceramics. Increasing the sintering temperature enhanced both density and grain growth, with the fine-grained structure proving essential for achieving a high dielectric constant (ε' ~ 2.2 × 10⁴) and maintaining low dissipation factors (tanδ ~ 0.011) at a reduced sintering temperature of 1150 °C. At an elevated sintering temperature of 1210 °C, optimal dielectric properties were observed, yielding ε' ~ 1.0 × 10⁴ and an ultra-low tanδ of ~ 0.004, attributed to highly resistive grain boundaries. The CP response is linked to semiconducting grains, supported by the presence of Ti³⁺ resulting from Ti⁴⁺ substitution by Nb⁵⁺. The minimal variation in ε' with temperature suggests suitability for capacitor applications, with ε' exhibiting little dependence on DC bias (0-30 V/mm). Optimized sintering conditions yielded stable CP properties with minimal sensitivity to humidity (30%-90% RH) over a range of temperatures (25-85 °C) and frequencies (10²-10⁶ Hz). These findings underscore the potential of (Sn_1/2Nb_1/2)_0.025Ti_0.975O₂ ceramics for advanced capacitors in varied environmental and operational conditions.