Effect of sintering temperature on the dielectric properties of 3D‐printed alumina (Al2O3) in the W‐band

• Published in: Journal of the American Ceramic Society 2024-04, Vol.107 (4), p.2494-2503
• Main Authors: Jenkel, Kai‐Daniel, Sánchez‐Pastor, Jesús, Baloochian, Mohammad Mahdi, Jakoby, Rolf, Sakaki, Masoud, Jiménez‐Sáez, Alejandro, Benson, Niels
• Format: Article
• Language: English
• Subjects: additive manufacturing; alumina; Aluminum oxide; Crystal structure; Dielectric loss; dielectric materials/properties; Dielectric properties; Material properties; Permittivity; Photonic crystals; sinter/sintering; Sintering; Temperature; Three dimensional printing
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.19597

This contribution discusses the impact of sintering temperatures on dielectric properties of 3D‐printed alumina (Al2O3) in the W‐band, by evaluating high quality factor (−Q) resonators integrated in a 2D photonic crystal structure. By varying the sintering temperature of the lithography‐based ceramic manufactured (LCM) samples, the microstructure of the material can be defined, which has a direct impact on the dielectric permittivity and material losses. Using a highly accurate photonic crystal structure, with a dimensional variation below 2% from print to print, an accurate extraction and evaluation of the dielectric material properties could be achieved. The relative permittivity of the alumina was tuned from 4.4 at 1250°C to 9.2 at 1650°C, whereas the observed change in dielectric losses was moderate. The maximum in observed dielectric loss for samples sintered at the lowest evaluated temperature, only yields an average value of 30 × 10−4. This demonstrates the versatility of the LCM technology for mm‐ and sub‐mm‐wave applications and its possibilities for material tuneability. Tuning of the porosity of 3D‐printed artificial dielectric material based on alumina was successfully implemented, enabling a fine adjustment of the permittivity in the range of 4–10. This closes the permittivity gap between additive‐manufactured dielectric materials and alumina mentioned in the literature. This was evaluated by changing the sintering temperature of additively manufactured high‐Q resonators.