Continuous Permittivity Tuning From 4 to 34 Using Low-Loss 3D-Printed Al ₂ O ₃ and ZrO ₂ for THz-Range Applications

In this contribution the influence of the porosity on 3D-printed ceramics, specifically Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and ZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, in terms of dielectric properties is analyzed at THz frequencies. By varying the porosity, i.e. the amount of air in the ceramic parts, an effective medium approach can be applied to tailor the material properties, such as the relative permittivity, over a wide range. Ceramics are fabricated using the lithography-based ceramic manufacturing (LCM) method, where printed green bodies are subjected to debinding and sintering to form the desired ceramic components. Here, the sintering temperature has a direct influence on the sample porosity and thus on its permittivity. Using this temperature variation concept, a relative permittivity tuning between 4.3 - 34.2 is demonstrated using a multi material approach including low loss Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as well as ZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>. Depending on the sample processing, the ceramic exhibits birefringence effects, which are investigated in dependence of sintering temperature.