Ag- and Li-Doped ZnO Nanostructures: Morphological Features and Piezoelectric Applications

The pursuit of sustainable and lead-free alternatives for piezoelectric materials has motivated the development of new synthesis strategies with minimal environmental impact. In this study, we report an eco-friendly approach for fabricating piezoactive nanostructures based on zinc oxide (ZnO) doped with silver (Ag) and lithium (Li).

The nanostructures were synthesized via a low-temperature hydrothermal method directly on metallic substrates (platinum and titanium foils) previously coated with a ZnO seed layer obtained through sol–gel spin coating. The hybrid system was further encapsulated with a polymer layer to ensure mechanical stability and compatibility for device integration. Comprehensive morphological characterization was performed using atomic force microscopy and scanning electron microscopy, confirming the successful growth of well-aligned doped ZnO nanostructures. The piezoelectric performance of the samples was evaluated through measurements of the direct piezoelectric coefficient (d₃₃).

The results demonstrated that the incorporation of dopant ions not only preserved but also enhanced the piezoelectric activity of the ZnO structures, indicating that the synthesis route is both efficient and environmentally responsible. This work highlights the potential of Ag- and Li-doped ZnO nanostructures, prepared under green processing conditions, for obtaining large-area piezoelectric materials. The combination of low-cost synthesis, ecological benefits, and functional piezoelectric response suggests that this approach represents a promising pathway toward sustainable materials design for applications in energy harvesting.