Structural evolution and microwave dielectric properties in Sr2(Ti1-xSnx)O4 ceramics

The structure and microwave dielectric properties of Sr2(Ti1-xSnx)O4 ceramics were determined in the entire composition range of x = 0-1.0. X-ray diffraction patterns and Raman spectra indicated a composition-induced onset of octahedral tilting at x = 0.75, and the crystal structure transformed from tetragonal (I4/mmm) to orthorhombic (Pccn). An obvious change of grain morphology was observed in the phase transformation region as well. The variations of the microwave dielectric properties with composition were systematically investigated and the effect of octahedral tilting on the evolution of τf value was emphasized. Moreover, the relationship between τε and tolerance factor of the present ceramics was revealed and compared with the empirical rule in perovskite structure. The role of tolerance factor in designing the materials with required performance was highlighted.