Structure-microwave property relations of Ca and Sr titanates

The microwave dielectric properties of the SrxCa1−xTiO3, Srn+1TinO3n+1 and (SrxCa1−x)3Ti2O7 series have been measured. TCF decreases from +1647 to +859 MK−1 as Ca content increases in the SrxCa1−xTiO3 series, due to the onset of octahedral tilt transitions. Additions of excess SrO to SrTiO3 form the Srn+1TinO3n+1 series with Q a maximum for Sr3Ti2O7. Ca substitutions to Sr3Ti2O7 result in a solid solution limited to the Sr and Ca rich ends of the (SrxCa1−x)3Ti2O7 series with Q a maximum of 10 250 at 2.5 GHz for Sr2.4Ca0.6Ti2O7 and TCF a minimum +50 MK−1 for Ca3Ti2O7. The variation of TCF for the (SrxCa1−x)3Ti2O7 series was also attributed to the onset of octahedral tilt transitions.