SrTiO₃ Cubes and Truncated Rhombic Dodecahedra Exhibiting Large Lattice and Piezoelectric Variations

Recognizing the existence of notable X-ray diffraction (XRD) peak shifts between SrTiO₃ cubes and {100}-truncated rhombic dodecahedra, their synchrotron XRD patterns were analyzed. Again significant peak shifts are present. Moreover, cubes give symmetric diffraction peaks, yet truncated rhombic dodecahedra exhibit peak splitting that can be deconvoluted into bulk and (110)- and (110)-related surface lattice components. Temperature-varying XRD measurements reveal different cell constant expansion and contraction behaviors for these two samples. Fast Fourier transform (FFT) processing of their high-resolution transmission electron microscopy (HR-TEM) images indicate a thinner surface layer lattice with considerable lattice point deviations for a truncated rhombic dodecahedron than that for a cube, explaining the observation of XRD peak splitting. The truncated rhombic dodecahedra also show much larger piezoelectric and ferroelectric responses than the cubes do. The diverse facet-dependent behaviors of SrTiO₃ crystals are linked to their interior lattice variations.