Electron microscopic and diffraction study of proton-exchanged LiNbO3

Abstract

Abstract The microstructure of proton-exchanged Li1-xHxNbO3 (x = 1) is observed by high-resolution electron microscopy, single crystal electron diffraction and powder X-ray diffraction. Fully-exchanged HNbO3, having perovskite-type structure (space group Pm3m; a = 3.822 A), may be obtained from fine powders. For single crystal material, another cubic phase Li1-xHxNbO3 is obtained, having a perovskite-related superstructure in space group Im3 (a = 7.645 A). The structural basis for this phase and the atomic mechanism involved in the proton-exchange reaction may be understood using the concept of chemical twinning and octahedral tilting.