Facile Synthesis and Conductivity Studies of Multifunctional [CGN]/[LNS] Composite Material as Relaxor Dielectric

In the present study, a composite material of doped ceria and lithium sodium sulphate for its structural and electrical properties was investigated for multipurpose applications. Analysis revealed composite to be capable of being used as relaxor dielectric, dielectric resonator antenna for radio signals, NTC thermistor, oxygen sensor, MOSFET, humidity sensor, multilayer capacitor, low sintering dielectric and electrolyte material in solid oxide fuel cells (SOFCs). Composite with a ratio of [Ce_0.5Gd_0.25Nd_0.25O_2−δ]_0.8 (CGN)/[(Li_0.8Na_0.2)₂SO₄]_0.2 (LNS) was prepared. The composite was sintered at 500 °C for 20 min. X-ray diffraction (XRD) revealed cubic crystal structure of CGN and hexagonal crystal structure of LNS. AC electrical properties including dielectric loss tangent (tanδ), dielectric constant (ε′), and ac electrical conductivity (σ_ac), were analysed for CGN and CGN/LNS as a function of frequency (20 Hz–3 MHz) at temperatures 30–400 °C. Moreover, ac electrical properties were also analysed as a function of temperature (30–650 °C) at a fixed frequency. Composite showed dielectric constant of 2.87 × 10⁵ at 400 °C and 1 kHz frequency. Composite showed a relaxor type behaviour. Composite also showed a maximum ac conductivity of 1.23 S m⁻¹ at 480 °C and minimum impedance of 3 Ω at 600 °C. Samples also showed proton conductivity at lower temperatures. Cole–cole plots were also studied for the composite. DC electrical conductivity and activation energy of CGN and CGN/LNS was analysed using two probes method in a temperature regime of 30–600 °C. DC conductivity increased from 0.005 to 0.25 S m⁻¹ in the composite (compared to single phase CGN) at 550 °C. Activation energy of the above-mentioned samples was also determined.