Dielectric Response, Non-Ohmic Behaviors and Humidity-sensing Characteristics: Tin Doping in Sodium Yttrium Copper Titanate Ceramics

Abstract

The impact of tin (Sn⁴⁺) doping on sodium yttrium copper titanate (Na_0.5Y_0.5Cu₃Ti₄O₁₂) ceramics, prepared using a conventional mixed-oxide route, was thoroughly investigated in terms of microstructure, dielectric properties, electrical response, non-linear behaviors, and humidity-sensing characteristics. All sintered ceramics showed a dense micro-structure and a pure Na_0.5Y_0.5Cu₃Ti₄O₁₂ phase without any secondary phases. The doped Na_0.5Y_0.5Cu₃Ti_4−xSn_xO₁₂ ceramics, with x = 0.05, demonstrated excellent dielectric properties, including a low dielectric loss tangent (∼0.032) and a giant dielectric permittivity (∼1.8 × 10⁴) across a wide temperature range. Sn⁴⁺ doping improved the non-linear behaviors at 25°C in Na_0.5Y_0.5Cu₃Ti₄O₁₂, with a reduced dielectric loss tangent corresponding to an enhanced grain boundary (GB) response. The colossal dielectric response is attributed to the internal barrier layer capacitor model, which relates to the Schottky barrier height (Φ_B) at the GBs. Notably, the Φ_B values for the Na_0.5Y_0.5Cu₃Ti₄O₁₂ ceramic increased with Sn⁴⁺ ion doping. Additionally, an in-depth study of the humidity-sensing properties of the Sn⁴⁺-doped Na_0.5Y_0.5Cu₃Ti₄O₁₂ material revealed that the capacitance at 1 kHz increased with increasing relative humidity levels, from 30% to 90%, suggesting potential applications in humidity-sensing technologies.