High dielectric constant in calcium-substituted GdMnO3 for storage device applications

Gd_0.7Ca_0.3MnO₃ and Gd_0.67Ca_0.33MnO₃ ceramics have been synthesized by solid-state reaction method at 950 °C. Crystalline nature and orthorhombic structure have been confirmed from the XRD analysis. Loosely packed grains of different shapes with small amount of porosity are observed from the SEM analysis. The room temperature dielectric constant of Gd_0.7Ca_0.3MnO₃ and Gd_0.67Ca_0.33MnO₃ samples are found to be 4775 and 318 with a dielectric loss factor of 1.48 and 2.40, respectively, at 1 kHz frequency. The observed room temperature dielectric constant value of Gd_0.7Ca_0.3MnO₃ is quite higher as compared to the dielectric constant values of substituted GdMnO₃ reported in the previous literatures. The observation of these dielectric values at room temperature with low dielectric loss factor makes both the materials suitable for applications in memory storage devices. Non-Debye type of relaxation mechanism has been confirmed from the impedance and modulus analysis. The optical energy band gap of Gd_0.7Ca_0.3MnO₃ and Gd_0.67Ca_0.33MnO₃ is found to be 3.1 eV and 2.89 eV, respectively.