ORALS
SESSION:
NanomaterialsThuAM-R3
| Echegoyen International Symposium (8th Intl. Symp. on Synthesis & Properties of Nanomaterials for Future Energy Demands) |
| Thu. 30 Nov. 2023 / Room: Dreams 3 | |
| Session Chairs: Miguel A. Alario Franco; Mark Hersam; Session Monitor: TBA |
11:35: [NanomaterialsThuAM01] OL
SIZE DOES MATTER… IN SOLID STATE CHEMISTRY¡ THE CASE OF THE RARE EARTHS Miguel A. Alario Franco1 ;
1Complutense U. of Madrid, Madrid, Spain;
Paper Id: 96
[Abstract] Knowing that solids are formed by atoms, and that atoms have, indeed, a size, it is no wonder that the size of atoms does influence the Chemistry of Solids. However, the way the atoms size makes its influence can be rather elaborate, even surprising¡. In the present lecture, after a brief introduction of atoms and ions sizes, we will present two examples of the marked influence of Rare Earth (RE) ions sizes in two very interesting cuprate families:
* The High Pressure/High Temperature Solid State Synthesis of Materials of the so-called rutheno-cuprate family: RuSr2RECu2O8 (The unexpected influence of the f-electrons)
* The presence, or absence, of superconducting properties in the family of partly substituted copper in YSrCuO: i.e. Mo0.3Cu0.7Sr2RECuO7+d. (Anion & cation order/disorder)
* The third example shows the correlation of P & T in the ordering in the A & B positions of a quadruple perovskite “Sr2RECu2IrO9-”.[3]
References:
1.-M.Á. Alario-Franco*, Rocío Ruiz- Bustos & A.J. Dos Santos-García Inorg. Chem. (2008) 47,146475-6481.
2.-Xabier Martínez de Irujo-Labalde, Esteban Urones-Garrote, Susana García-Martín & Miguel Ángel Alario-Franco*: Inorg. Che .(2018) 57, 19, 12038-12049.
3.- M.Á. Alario-Franco et al, Turning points in Solid State Materials. RSC Publishing (2008)151-164
SESSION:
SolidStateChemistryTueAM-R4
| Poeppelmeier International Symposium(3rd Intl Symp on Solid State Chemistry for Applications & Sustainable Development) |
| Tue. 28 Nov. 2023 / Room: Dreams 4 | |
| Session Chairs: Shiv Halasyamani; Session Monitor: TBA |
12:25: [SolidStateChemistryTueAM03] OL
THE COMPLEX STRUCTURE & MICROSTRUCTURE OF “CUBIC” PBCRO3 Miguel A. Alario Franco1 ;
1Complutense U. of Madrid, Madrid, Spain;
Paper Id: 95
[Abstract] PbCrO3 perovskite was first synthesized by Roth and deVries in the late 1960s [1]. Chamberland and Moeller [2] also synthesized PbCrO3 and their structural results were in agreement with the previous ones but, in addition, reported an unusual broadening of the diffraction peaks even using monochromatic CuKa1 radiation. These broad lines in the X-ray powder patterns were also observed for the same compound by Goodenough et al. [3]. However, in these works neither atomic concentration nor microstructural studies were considered and/or analyzed. A rather puzzling situation concerning the 3d-metal, (4+) lead-based perovskites, resides in the fact that while PbTiO3 is tetragonal with c/a 1⁄4 1.064 and ferroelectric with Tc763 K [4], and PbVO3 is also tetragonal with a higher tetragonality factor, c/a 1⁄4 1.229 [3,4], PbCrO3 has been described as cubic. This is unexpected as in terms of ionic size the following trend is observed: VIr4+Cr< VIr4+V< VIr4+Ti, (0.55, 0.58, and 0.605 A, respectively [4]). Thus, one could expect that PbCrO3 should be even more tetragonal since the Cr(IV)–O bond would be more covalent. We have performed a structural and microstructural study using XRD, selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) to elucidate the origin of the abnormal broadening of the XRD maxima and to clarify the origin of the cubic structure of PbCrO3. In this way, it is shown that the lead-perovskite compound ‘‘PbCrO3’’ has a Pb deficiency, resulting in a modulated structure within a complex microdomain texture.
References:
[1] W.L. Roth, R.C. DeVries, J. Appl. Phys. 38 (1967) 951.
[2] B.L. Chamberland, C.W. Moeller, J. Solid State Chem. 5 (1972) 39.
[3] R.V. Sphanchenko, V.V. Chernaya, A.A. Tsirlin, P.V. Chizhov,, D.E. Sklovsky, E.V. Antipov, Chem. Mater. 16 (2004) 3267.
[4] A.A. Belik, M. Azuma, T. Saito, Y. Shimakawa, M. Takano, Chem. Mater. 17 (2005) 269.
