Structural properties and phase transformation of sol–gel prepared lanthanum tantalates

• Published in: Journal of materials science Vol. 49; no. 24; pp. 8423 - 8435
• Main Authors: Bruncková, H., Medvecký, Ľ., Ďurišin, J., Hvizdoš, P., Girman, V.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.12.2014; Springer; Springer Nature B.V
• Subjects: Agglomerates; Analysis; Annealing; Characterization and Evaluation of Materials; Chelation; Chemistry and Materials Science; Classical Mechanics; Clusters; Crystallization; Crystallography and Scattering Methods; Differential scanning calorimetry; Diffraction; Diffraction patterns; Electron diffraction; Ethanol; Fluorite; Fourier transforms; Infrared analysis; Lanthanum; Materials Science; Methanol; Morphology; Nanoparticles; Original Paper; Perovskite; Perovskites; Phase transitions; Polymer Sciences; Precursors; Raman spectroscopy; Roasting; Scanning electron microscopy; Solid Mechanics; Solvents; Transmission electron microscopy; Tungsten bronze; X-rays; Tartrate; Perovskite; TaCl5; Tartaric Acid; Citric Acid
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-014-8552-1

Perovskite lanthanum tantalate La 1/3 TaO 3 (LT) precursors were prepared by a new polymeric complex sol–gel method using Ta-citrate or -tartrate complexes in different solvents (ethanol or methanol) and calcination between 750 and 1050 °C. The structural properties of precursors were characterised by X-ray diffraction (XRD), differential scanning calorimetry / thermogravimetric analysis (DSC/TG), Fourier transform infrared (FTIR) and Raman spectroscopy, scanning and transmission electron microscopy (SEM, TEM). The fluorite orthorhombic tungsten bronze (TB) of La 4.67 Ta 22 O 62 and perovskite La 1/3 TaO 3 phases with a small amount of pyrochlore monoclinic LaTaO 4 phase were formed after calcination at 900–1050 °C respectively, irregardless of solvent. The particle morphology changed from larger agglomerates composed of spherical 5–20 nm amorphous clusters without visible crystallization at 750 °C to plate-like shaped of well-ordered LT nanoparticles (ethanol) or individual spherical clusters with the fine inner structure (methanol) at 1050 °C. The same effect of alcohol solvent on phase transformation during annealing was shown, whereas the effect of chelating agent was insignificant. Graphical Abstract Selected area electron diffraction (SAED) patterns of La 1/3 TaO 3 precursors after calcination at 900 °C ( a ) metastable fluorite La 4.67 Ta 22 O 62 , ( b ) perovskite La 1/3 TaO 3 and ( c ) LaTaO 4 phases and ( d ) multidomain structure of super cell of La 2/3 Ta 2 O 9 .