Structural analysis of ceramic compounds of the solid solutions Sr Ti(1-x) Rux O3 and Ca(1-x) Srx Ru O3

Full text. Ceramic compounds with perovskite structure of the type AMO3 (A=Ca, Sr) (M = Ti, Ru) have become a renewed attention in the last two years, due to their very interesting physical and chemical properties (Grupp et al., 1997 SCIENCE, vol. 276, 392), (Shepard et all., 1997, J. Appl. Phys., vol. 81, part 2B, 4978), (Rao et all., 1997, Appl. Phys. Lett., vol. 70, 3035), (Kiyama et all., 1996, Phys. Rev. B 54, 756). Recent works have been published on the possible technological applications of these compounds as metallic perovskite substrates in epitaxial structures (Ahn et all., 1997 SCIENCE, vol. 276, 100). We study the structural behaviour of both solid solutions through X-ray powder diffraction using the Rietveld Method to refine the crystal structures. preliminary refinements were performed with data collected with an X-ray rotating anode source. For Sr Ti (1-x) Ru x O3 the results indicated that at lower contents of Ru (x = 0.01 to 0.3) the compounds have still a cubic symmetry Pm 3 m like Sr Ti O3. At high contents of Ru ( x = 0.001 to 0.3)the compounds have still a cubic symmetry Pm 3 m like Sr Ti O3. At high contents of Ru ( x= 1,0.8, 0.5) the symmetry is orthorhombic Pnma. A cubic-orthorhombic structural transition takes place at the intermediate compositions with x = 0.33 and 0.4. Synchrotron radiation powder diffraction data were collected at LNLS with the purpose of determine precisely the structure and possible phase transitions, as well as to classify the tilt systems of these complex perovskites. Furthermore, we present a discussion about the relationships between the structural phase transition and electric resistivity measurements in Sr Ti(1-x) Rux O3. (author)