ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Sr substitution impact on the crystal structure and electrophysical properties of the phases on the base of BaNd₂In₂O₇

Y. A. Titov, N. N. Belyavina, M. S. Slobodyanik, O. I. Nakonechna, N. Yu. Strutynska, and R. N. Kuzmin

Taras Shevchenko National University of Kyiv, Kyiv, Ukraine

E-mail: Strutynska21.05@gmail.com

Received: 6 April 2022  Accepted: 15 July 2022

Abstract:

The effect of isomorphic substitution of atoms on crystal structure and properties of oxide compounds is one of the main tasks of modern materials science. This work is devoted to the study of Ba atoms by smaller Sr atoms’ substitution in two-slab perovskite-like structure of BaNd₂In₂O₇ and its effect on the structural features and electroconductive properties of the Ba_1−xSr_xNd₂In₂O₇ indates synthesized. A characterization, including data of X-ray diffraction, structural calculations (Rietveld method) of phases obtained, is presented. Existence region of Ba_1−xSr_xNd₂In₂O₇ solid solutions with a two-slab perovskite-like structure (0 ≤ x ≤ 0.2) was established and their coordinate parameters (x = 0.1 and x = 0.2) are refined. Ba_1−xSr_xNd₂In₂O₇ structure is based on two-dimensional (infinite in the XY plane) perovskite-like blocks of two slabs connected by vertices of deformed InO₆ octahedra. Neighbouring blocks are separated by a slab of NdO₉ polyhedra and interconnected by O–Nd–O bonds. Correlations between substitution degree of barium atoms and electroconductive properties have been established. It is shown that such type of substitution leads to a decrease in the Nd–O2 interblock bond length (from 0.223(2) nm at x = 0 to 0.214(1) nm at x = 0.2). This brings the constitution of two-dimensional structure of Ba_1−xSr_xNd₂In₂O₇ closer to the structure of three-dimensional perovskite and leads to its destruction at x > 0.2. Increase in the degree of substitution is also accompanied by a gradual decrease in specific conductivity of ceramic grains and increase in the activation energy and their own electrical conductivity.

Keywords: Compounds of An+1BnO3n+1 type; Slab perovskite-like structure; Interblock distance; Polyhedron deformation; Impedance spectroscopy

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02380-0

Chemical Papers 76 (11) 6931–6939 (2022)