Premium
One‐dimensional contrast modulations in [001] high‐resolution reverse images of Bi 2 Sr 2 (Ca 1− x Nd x )Cu 2 O 8+δ ceramics
Author(s) -
Onozuka T.
Publication year - 1993
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889892009142
Subject(s) - contrast (vision) , resolution (logic) , materials science , high resolution , crystallography , optics , chemistry , physics , geology , remote sensing , computer science , artificial intelligence
The one‐dimensional contrast modulation along the b axis of [001] high‐resolution reverse images of the compounds Bi 2 Sr 2 (Ca 1 − x Nd x )Cu 2 O 8 + δ ( x = 0.05 + 0.1 n ; n = 1, 2, 6 and 7) is examined closely using the density distribution recorded from a wide area of the negative film by microphotometric densitometry. Three typical short units of the density distribution, of lengths 4.5 b 0 , 5 b 0 and 4 b 0 , characterized by twin peaks or a single maximum peak with subpeaks in the middle of the unit, are discerned. The density distributions of the three units and the contrast modulations of their images are reproduced well by computer simulations, using three structure models modulated with longitudinal displacement waves along the b axis of the metal atoms. The one‐dimensional contrast modulation is attributed to sinusoidal changes in the effective scattering amplitudes for the [001] electron beam of the metal‐atom chains along the c axis. The results of the simulation are applied to investigation of the (2, 1) 5 and (3, 1) 4 modulation modes in the modulated structure.