Structural characterization of a new acentric Ruddlesden-Popper layered perovskite compound: LiHSrTa2O7

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 39; no. 13; pp. 3212 - 3218
• Main Authors: Galven, Cyrille, Fourquet, Jean-Louis, Suard, Emmanuelle, Crosnier-Lopez, Marie-Pierre, Le Berre, Françoise
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.01.2010
• Subjects: Chemical Sciences; Cristallography; Inorganic chemistry
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/b921017m

A new n = 2 member acentric Ruddlesden-Popper layered perovskite LiHSrTa(2)O(7) (LiDSrTa(2)O(7)) has been synthesized and structurally characterized from Rietveld treatment of its powder X-ray and high-resolution neutron diffraction data. It can be synthesized by a partial Li(+)/H(+) exchange from the mother phase Li(2)SrTa(2)O(7) either in solid state by NH(4)Cl or in dilute HNO(3) by controlling the amount of H(+). This compound crystallizes in the orthorhombic acentric space group Ama2 (no. 40) with lattice constants a = radical2a(p) approximately 5.5522(1) A, b = radical2a(p) approximately 5.5248(1) A and c approximately 18.7745(4) A. Classically, Ta(5+) ions occupy the octahedral sites of the kinked perovskite blocks and Sr(2+) ions completely fill the perovskite cages while Li(+) and D(+) ions are found in the interlayer spacing. Efficient positive second harmonic generation response, performed at room temperature on a polycrystalline sample, shows unambiguously the acentric character of this new phase. Interestingly, the choice of the acentric Ama2 space group to describe the structure is revealed only by high-resolution neutron diffraction data: in the interlayer spacing, Li(+) and D(+) cations are unequally distributed on different sites (two 4a sites for Li(+) and two 4b sites for D(+) ions).