3D printing of infrared transparent ceramics via material extrusion

Fabrication of transparent ceramics with complex geometric structure by 3D printing break through the limitations of traditional ceramic molding process, thus gained increasing research interest. Till now, 3D printing transparent ceramics are limited to visible transparent systems. Herein, 3D printed infrared transparent 3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia) ceramics are achieved for the first time by material extrusion (MEX). We developed an aqueous ceramic ink with high solid content (ϕ) up to 50 vol% and excellent shear thinning properties (n = 0.1975) for MEX. By using this ceramic ink, a hemispherical dome cover with a convex radius of curvature (R) of 6.5 mm, a concave radius of curvature (r) of 5.5 mm, and thickness of 1 mm and a flat disc (R =10 mm) with were successfully printed. The relative density up to 99.85% was obtained after de-binding and two-step sintering process including pre-sintering and hot isostatic pressing (HIP). Such high relative density enables its high transparency (>70%) in the mid-infrared (3–5 µm) region. Vickers hardness for the 3D printed infrared transparent ceramic was determined as 14.583 ± 0.379 GPa.