Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]− layers

A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450–550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]− layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

Graphical abstractA new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450–550 °C. It is isostructural with LiNbO2 with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. Mg2+ are described in spheres located between [NbO2]− trigonal layers and its occupancy is 0.5.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2. ► Cation-exchange reaction converted two monovalent Li+ into one divalent Mg2+ at 450–550 °C. ► Mg0.5NbO2 was isostructural with LiNbO2 (space group; P63/mmc). ► Its lattice parameters were a=2.9052(6) Å and c=10.625(15) Å. ► Synthesized Mg0.5NbO2 was calculated to be thermodynamically more favorable.