Evaluation of recovered Yttria – stabilized Zirconia as a solid loading for ceramic – based 3D printing of solid oxide cell electrolytes

This master thesis explores the suitability of recycled ceramics materials for applications such as electrolytes in Solid Oxide Cells (SOC), focusing on their production using 3D printing techniques, such as Robocasting (RC). Combining recovery strategies for critical raw materials (CRM) with additive manufacturing technologies represents an underexplored research area. This work evaluates the main challenges of combining these two technologies to produce a 3D–printed electrolyte for SOC application. The study is based on an extensive characterisation of the recycled ceramics materials, evaluating their structural, thermal, and electrochemical properties and their 3D printability. Recycled powders from End–of–life (EoL) SOCs were produced via a chemical process and recovered at 3% mol. Yttria Stabilized Zirconia (3YSZ) derived from mechanical processing for dental prostheses were used in this work as examples of different recycling/recovery pathways and are presented in the introductory section. The characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), Hot Stage Microscopy (HSM) and electrochemical tests; these techniques are presented in the experimental method section, with particular focus on the particle size distribution and residuals of unwanted elements. This section also discusses the formulation process for RC for ceramic pastes, presenting the feedstock material's main requirements, components, and polymerization process. The results section shows that materials obtained from recycling/recovery pathways can potentially be used as electrolytes produced via 3D printing for SOC applications, although optimization of their composition and sintering conditions is required to improve their performance. Furthermore, the analysis of 3D printing highlights the challenges in paste formulation and in adapting processing parameters to ensure the fabrication of electrolytes with adequate density and conductivity. The conclusions emphasize the potential of using recycled materials in combination with 3D printing technologies to prepare SOC electrolytes, promoting a sustainable approach for reducing technological waste and creating new supply chains for critical materials. However, further studies are necessary to refine recovery methods and manufacturing strategies to maximize the effectiveness of the materials in SOC applications.