Structural Study of La_1–<i>x</i>Y_<i>x</i>ScO₃, Combining Neutron Diffraction, Solid-State NMR, and First-Principles DFT Calculations

Abstract

The solid solution La_1–<i>x</i>Y_<i>x</i>ScO₃ (<i>x</i> = 0, 0.2, 0.4, 0.6, 0.8, and 1) has been successfully synthesized using conventional solid-state techniques. Detailed structural characterization has been undertaken using high-resolution neutron powder diffraction and multinuclear (⁴⁵Sc, ¹³⁹La, ⁸⁹Y, and ¹⁷O) solid-state NMR and is supported by first-principles density functional theory calculations. Diffraction data indicate that a reduction in both the unit cell parameters and unit cell volume is observed with increasing <i>x</i>, and an orthorhombic perovskite structure (space group <i>Pbnm</i>) is retained across the series. ⁴⁵Sc multiple-quantum (MQ) MAS NMR spectra proved to be highly sensitive to subtle structural changes and, in particular, cation substitutions. NMR spectra of La_1–<i>x</i>Y_<i>x</i>ScO₃ exhibited significant broadening, resulting from distributions of both quadrupolar and chemical shift parameters, owing to the disordered nature of the material. In contrast to previous single-crystal studies, which reveal small deficiencies at both the lanthanide and oxygen sites, the powder samples studied herein are found to be stoichiometric