composite thick films have been investigated regarding their suitability as low-temperature sintered tunable microwave dielectrics. The investigations showed that already a small amount of ZnO-B 2 O 3 additive can remarkably reduce the sintering temperature down to 900°C. Microstructural investigations of the thick films revealed the formation of an amorphous intergranular phase and a clustering of particles for high additive amounts. The microwave characterization showed a reduction in relative permittivity, dielectric loss, and tunability of the thick films with increasing additive content. These results demonstrate the potential to tailor the material abilities by varying the additive content.