Multifunctional Behavior of GdCa ₂ Cu ₃ O <i> _δ </i> for Capacitor and Thermistor Applications

ABSTRACT Ceramic‐based material GdCaCuO (GdCa 2 Cu 3 O δ ) was synthesized via the solid‐state reaction method and comprehensively characterized for its multifunctional properties. Structural, dielectric, and magnetic analyses were conducted to evaluate its potential use in capacitor and negative temperature coefficient (NTC) thermistor applications. The material exhibits a colossal dielectric permittivity and displays thermally stable capacitance across a wide temperature range (‒30°C to 105°C), aligning it with the Y5R‒Y6R dielectric classification standards recognized for their thermal stability in capacitive devices. Electrical resistivity measurements, carried out over the 300–570 K range, revealed a negative temperature coefficient of resistance (NTCR), characteristic of thermistor behavior. Two distinct thermistor constants were determined: β 1 = 2494 K (300–550 K) and β 2 = 7821 K (550–570 K). The stability factor was calculated to be 1.88, indicating moderate resistance variability, which is suitable for sensor integration. The corresponding sensitivity factors, α 1 (‒1% to ‒2.7%) and α 2 (‒2.3% to ‒2.7%), further validate the NTC thermistor performance. Magnetic characterization showed Curie–Weiss behavior. The compound was identified as an antiferromagnetic insulator, with Cu 2+ ( S = 1/2) spins undergoing long‐range antiferromagnetic ordering at a Neel temperature ( T N ) of 25 K. Electron paramagnetic resonance (EPR) measurements revealed a symmetric signal at g = 2.09 at room temperature, suggesting the presence of localized, unpaired electrons within a paramagnetic environment. This work aims to design and investigate a multifunctional GdCa 2 Cu 3 O δ ‐based ceramic material, with a particular focus on its dielectric, thermistor, and magnetic properties, to assess its suitability for capacitor and NTC thermistor applications.