Effect of Sn Substitution on Cation Ordering in (Zr1-xSnx)TiO4 Microwave Dielectric Ceramics

The crystal structure and microwave dielectric properties of (Zr1–xSnx)TiO4 ceramics with x ranging from 0.0 to 0.15 have been investigated to characterize the effect of Sn substitution on cation ordering and the effect of ordering on dielectric loss. The crystal structure of the samples was investigated using high‐resolution transmission electron microscopy and electron diffraction. Although Sn substitution inhibits ordering, the effect is progressive and ordering still proceeds to an observable degree in samples with x= 0.15. The ordered structure of all samples is of the incommensurate modular type previously observed for Sn‐free zirconium titanate compositions. In this structure individual (100) cation layers are observed to switch abruptly from Zr‐rich to Ti‐rich occupancy, indicating that ordering proceeds by the segregation of Zr and Ti into elongate two‐dimensional domains on (100). The domains get smaller as the Sn content of the samples increases and in Zr0.5Sn0.15TiO4 the length scale of the cation correlations is approximately 25–50 Å. We propose that the decrease in the driving energy for the coarsening of the domains during the ordering transformation is due to the preferential segregation of Sn to the Zr‐Ti domain boundaries. Whereas the long‐range cation ordering increases the dielectric loss of Sn‐free ceramics by 30%, it results in a negligible change in the loss properties of Zr0.91Sn0.09TiO4. It is possible that the hypothesized effect of Sn in stabilizing the Zr‐Ti boundaries may also affect the contribution of these sites to the dielectric loss of the ordered structures.