Mechanical and dielectric properties of (ZnSn)1-xMxO (M = Co, Cu) quaternary nanocomposites for promising applications

This study investigates the mechanical, elastic wave, AC conductivity, and dielectric properties of (ZnSn)₁₋ₓMₓO nanocomposites (NCs), where M is Co or Cu (0.00 < x < 0.50), and compares them to those of ZnO and SnO nanosheets. Both Co and Cu series NCs showed minor changes in mechanical and elastic wave propagation up to x = 0.30. ZnSnO NCs exhibited higher AC conductivity and dielectric constants than ZnO or SnO nanosheets, which were subsequently reduced by incorporating Co or Cu ions. While ZnSnO NCs displayed high dielectric loss (tan δ), Co incorporation led to lower tan δ without affecting the quality factor (Q_factor); conversely, Cu significantly decreased tan δ and strongly improved the Q_factor. The conduction mechanism shifted from polaron in ZnO or SnO nanosheets to hole-dominated in ZnSnO and Co-doped ZnSnO NCs, whereas the Cu-doped ZnSnO NCs exhibited a mixed polaron and hole conduction depending on the incorporated Cu content. ZnSnO NCs demonstrated lower bulk impedance and electronic polarizability than binary ZnO and SnO nanosheets; however, doped ZnSnO NCs with high Co concentration dramatically increased both, a trend opposite to that observed with Cu. Effective capacitance (C_eff) was significantly enhanced in ZnSnO NCs relative to binary ZnO and SnO nanosheets, followed by C_eff decrease with the addition of Co or Cu ions. Conversely, the electric modulus of ZnSnO NCs was considerably reduced compared to SnO or ZnO nanosheets, and this reduction was further amplified by Co or Cu incorporation. Parameters such as polaron binding energy and hopping distance were estimated using the correlated barrier polaron hopping modelVariations in properties between nanosheets and NCs are primarily attributed to differences in internal structures. Notably, these (ZnSn)_1-xMₓO NCs, both undoped and doped with Co or Cu, show promise for energy storage applications.