TY - JOUR AU - Titov, Y.A. AU - Belyavina, N.M. AU - Slobodyanik , M.S. AU - Nakonechna, O.I. AU - Strutynska , N.Yu. AU - Chumak , V.V. PY - 2022/12/23 Y2 - 2024/03/29 TI - Effect of isovalent substitution on structure of the two-slab BaNd2-xSmxIn2O7 indates : Array JF - Physics and Chemistry of Solid State JA - Phys. Chem. Sol. State VL - 23 IS - 4 SE - Scientific articles (Chemistry) DO - 10.15330/pcss.23.4.801-808 UR - https://scijournals.pnu.edu.ua/index.php/pcss/article/view/6231 SP - 801-808 AB - <p>The conditions of isovalent substitution of Nd atoms for Sm atoms in <em>A</em>-positions of the BaNd<sub>2</sub>In<sub>2</sub>O<sub>7</sub> two-slab perovskite-like structure of the BaNd<sub>2-x</sub>Sm<sub>x</sub>In<sub>2</sub>O<sub>7</sub> type (0 £ <em>x</em> £ 1.8) have determined by X-ray powder diffraction methods. Tetragonal crystal structure (space group <em>P4<sub>2</sub>/mnm</em>) of the BaNd<sub>2-x</sub>Sm<sub>x</sub>In<sub>2</sub>O<sub>7</sub> phases with substitution degree of Nd atoms equal to 0.5, 1.0, 1.5 and 1.8 was determined by the Rietveld method. Crystal structure of BaNd<sub>2-x</sub>Sm<sub>x</sub>In<sub>2</sub>O<sub>7</sub> is based on the two-dimensional (infinite in the <em>XY</em> plane) perovskite-like blocks, consisting of two slabs of the deformed InO<sub>6</sub> octahedra connected by vertices. Ba atoms are localized only at 4<em>f</em> position inside the perovskite block, while REE atoms are placed only at 8<em>j</em> position at the boundary of the perovskite block. The adjacent perovskite-like blocks are separated by a slab of LnO<sub>9</sub> polyhedra and held together by - O - Ln - O - interblock bonds. It is established that the isovalent substitution of Nd atoms by smaller Sm atoms leads to a decrease in the length of the Ln - O2&nbsp; distance (from 0.230(2) nm to 0.206(2) nm) and to an increase in the degree of deformation of the interblocks of LnO<sub>9</sub> polyhedra, the inner block polyhedra BaO<sub>12</sub>, and the InO<sub>6</sub> octahedra as well. Such structural changes destabilize the interblock "stitching" and are one of the main destruction factors of the slab&nbsp; &nbsp;perovskite-like structure of the BaNd<sub>2-x</sub>Sm<sub>x</sub>In<sub>2</sub>O<sub>7</sub> phases at <em>x</em> &gt; 1.8. Data obtained could be used for directed regulation of structure-sensitive properties of materials based on the BaNd<sub>2</sub>In<sub>2</sub>O<sub>7</sub> indate.</p> ER -