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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.