Formation of complex alkoxides to control layer structure in Sr-Bi-M-O (M: Ta or Nb) perovskite thin films

• Published in: Journal of materials science. Materials in electronics 1998-12, Vol.9 (6), p.457-464
• Main Authors: Kato, K, Zheng, C, Finder, J M, Dey, S K, Torii, Y
• Format: Article
• Language: English
• Subjects: Crystallites; Electronics; Niobium; NMR; Nuclear magnetic resonance; Perovskites; Precursors; Strontium; Tantalum; Thin films
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1023/A:1008906209683

Precursors for layer-structured perovskite thin films of Sr^sub 2^Bi^sub 2^Ta^sub 3^O^sub 12.5^ or SBT223, and Sr^sub 2^Bi^sub 2^Nb^sub 3^O^sub 12.5^ or SBN223 were prepared by the reactions of Sr-Bi (2 : 2) double methoxyethoxide and Ta or Nb methoxyethoxide, followed by partial hydrolysis. By several analytical techniques, such as ^sup 1^H-, ^sup 13^C- and ^sup 93^Nb-NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infrared) the molecular structure of the precursors was found to be similar to the layer-structured perovskite crystal sub-lattice. As a result, the onset of crystallization in the sol-gel derived SBT223 thin films was at a low temperature of 550°C. By rapid thermal annealing in an oxygen atmosphere, the single-phase perovskite films exhibited preferred (1 1 7) orientation. In contrast to the SBT system, the observed number of the pseudo-perovskite layers of TaO^sub 6^ octahedral units between Bi^sub 2^O^sub 2^^sup 2^ ^sup +^ layers in the SBT223 was three. Despite the elongation of the unit cell along the c-axis, 700°C-heated SBT223 thin film did not exhibit a saturated hysteresis loop due to the small crystallite size.[PUBLICATION ABSTRACT]