A labile hydride strategy for the synthesis of heavily nitridized BaTiO3

Abstract

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N(3-) species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H(-) in BaTiO3-xHx (x ≤ 0.6) allows H(-)/N(3-) exchange to occur, and yields a room-temperature ferroelectric BaTiO3-xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds.

Unconventional Luminescent Centers in Metastable Phases Created by Topochemical Reduction Reactions

“…To date,aseries of material systems,such as LaNiO 2 ,SrFeO 2 ,LaSrCoO 3 H 0.7 ,and BaTiO 3Àx H x ,h ave been prepared through this route. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Previous efforts have focused on the investigation of magnetic compounds containing transition-metal ions, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]19] and little attention has been paid to materials containing rare-earth ions. [18] As far as we are aware,t he use of topochemical reaction for the controlled synthesis of functional materials containing heavier p-block metal ions has never been explored.Novel luminescent materials emitting in the near-infrared (NIR) spectral region are urgently needed in connection with applications for bioimaging and telecommunications.L uminescent materials containing bismuth, one of the most investigated p-block elements,h ave attracted significant research interest owing to their importance in both fundamental science and practical applications for solid-state lighting, bioimaging,l asers,a mplifiers,a nd detectors.…”

“…Abstract: Al ow-temperature topochemical reduction strategy is used herein to prepare unconventional phosphors with luminescence covering the biological and/or telecommunications optical windows.This approach is demonstrated by using Bi III -doped Y 2 The development of functional materials has long benefited from advances in synthetic strategies.A si sw ell known, conventional high-temperature synthetic routes can be used to prepare ab road spectrum of complex oxides with thermodynamically stable phases,p recluding the formation of metastable materials.Inmarked contrast, low-temperature topochemical reduction reactions have allowed the preparation of complex transition-metal-oxide phases bearing highly unusual oxidation states and coordination geometries,attracting tremendous attention in the field of solid-state chemistry. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Theprinciple advantage of this "soft" chemical route lies in the fact that it is driven by kinetics,t hus allowing rational design of structures and compositions as metastable products at considerably lower reaction temperatures than when conventional techniques are used. To date,aseries of material systems,such as LaNiO 2 ,SrFeO 2 ,LaSrCoO 3 H 0.7 ,and BaTiO 3Àx H x ,h ave been prepared through this route.…”

Unconventional Luminescent Centers in Metastable Phases Created by Topochemical Reduction Reactions

“…As is well known, conventional high‐temperature synthetic routes can be used to prepare a broad spectrum of complex oxides with thermodynamically stable phases, precluding the formation of metastable materials. In marked contrast, low‐temperature topochemical reduction reactions have allowed the preparation of complex transition‐metal‐oxide phases bearing highly unusual oxidation states and coordination geometries, attracting tremendous attention in the field of solid‐state chemistry . The principle advantage of this “soft” chemical route lies in the fact that it is driven by kinetics, thus allowing rational design of structures and compositions as metastable products at considerably lower reaction temperatures than when conventional techniques are used.…”

Selective Partial Substitution of B‐Site with Phosphorus in Perovskite Electrocatalysts for Highly Efficient Oxygen Evolution Reaction

“…Perovskite oxides with the employment of non‐metal elements such as phosphorus (P),, sulfur (S),, nitrogen (N), and fluorine (F) have been developed for improving the electrochemical/photocatalytic activity. Zhu et al.…”