A comprehensive investigation of the structural, chemical, and dielectric properties of co-doped YMnO${}_3$ multiferroic component

The solid-state reaction technique was employed to synthesize compounds of YMnO${}_3$ (YMO) and YMn${}_{1-x}$Co${}_x$O${}_3$ (YMCO) with various Co doping levels (x = 0.01, 0.10, 0.20, and 0.40), where Co atoms partially substituted Mn sites. XRD studies confirmed the presence of two phases, YMO and Y${}_{0.98}$CoO${}_3$ (YCO), for doping ratios above x = 0.10. Additionally, an increase in crystalline size was observed with cobalt substitution. Surface characteristics of synthesized pellets were examined using scanning electron microscopy (SEM), revealing a less porous structure with cobalt doping. XPS analysis elucidated valence states, showing the presence of both Mn${}^{3+}$ and Mn${}^{4+}$, as well as Co${}^{2+}$ and Co${}^{3+}$. The x = 0.20 and 0.40 Co-doped samples exhibited lower grain and grain boundary energies compared to other samples, such as a decrease from 0.556 eV (undoped) to 0.195 eV (x = 0.20). Moreover, the dielectric constants of x = 0.20 and 0.40 cobalt-doped samples (around 320) significantly surpassed the undoped sample (around 22) at 10${}^6$ Hz and 100 °C. The x = 0.20 cobalt-doped sample demonstrated the highest conductivity at 100 °C and 10${}^6$ Hz (31 × 10${}^{-4}$ S/cm). FT-IR analysis provided insights into vibration and bending modes, and frequency- and temperature-dependent electrical features were investigated. It was observed that a single conduction model is insufficient to fully explain the conduction mechanism in these samples.