ZrO 2 -SnO 2 -TiO 2 solid solutions, specially (Zr 0.8 Sn 0.2 )TiO 4 , are important compositions for use in resonators at microwave frequency because of their inherent characteristics. However, their high sintering temperature makes it difficult to reach a well densified structure. In this research, effects of CuO as a sintering aid were studied. Solid state reaction of primary oxides and CuO (1, 1.5, 2 and 2.5wt%) showed that CuO could reduce sintering temperature, effectively. Increase in CuO content, which is accompanied by increase in grain boundary liquid phase, promotes dielectric properties. Changes in density up to 2 wt%CuO-doped samples, had the same trend as the amount of additive and for 2.5 wt%CuO-doped samples, this value decreased slightly because of liquid phase vapourization. No second phase containing Cu or Zn ions was detected by XRD. Changes in lattice parameters and unit cell volume of the compounds, caused some changes in dielectric properties. In addition, this additive could not accelerate cation ordering in structure. The results show that addition of CuO up to 2.5wt%, has increased Q value up to 6905. Annealing at the same temperature showed that re-activation and rearrangement of liquid phase, accompanied by changes in grain size, cation ordering, density and lattice parameters, would improve dielectric properties of CuO-doped (Zr 0.8 Sn 0.2 )TiO 4 and achieve Q=7575 for 2.5 wt%CuO-doped samples.
