Layered-structural monoclinic–orthorhombic perovskite La{sub 2}Ti{sub 2}O{sub 7} to orthorhombic LaTiO{sub 3} phase transition and their microstructure characterization

• Published in: Materials characterization Vol. 89
• Main Authors: Herrera, G., Departamento de Química Inorgánica, Universidad de Valencia, 46100 Burjasot, Valencia, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, 04510 México D. F., Jiménez-Mier, J., Chavira, E.
• Format: Journal Article
• Language: English
• Published: United States 01.03.2014
• Subjects: ACRYLAMIDE; ATOMIC FORCE MICROSCOPY; CERAMICS; DIELECTRIC MATERIALS; DIFFERENTIAL THERMAL ANALYSIS; LANTHANUM; LANTHANUM COMPOUNDS; MATERIALS SCIENCE; MECHANICAL PROPERTIES; MICROSTRUCTURE; MONOCLINIC LATTICES; NANOCOMPOSITES; NANOSCIENCE AND NANOTECHNOLOGY; ORTHORHOMBIC LATTICES; PEROVSKITE; PHASE TRANSFORMATIONS; POLYMERIZATION; SCANNING ELECTRON MICROSCOPY; SPACE GROUPS; TITANATES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION
• DOI: 10.1016/J.MATCHAR.2013.12.013
• ISSN: 1044-5803

The layered-structural ceramics, such as lanthanum titanate (La{sub 2}Ti{sub 2}O{sub 7}), have been known for their good temperature and low dielectric loss at microwave frequencies that make them good candidate materials for high frequency applications. However, few studies have been conducted on the synthesis optimization by sol gel reaction, in particular by acrylamide polymerization route. The interest in La{sub 2}Ti{sub 2}O{sub 7} ceramic has been greatly increased recently due to the effect of oriented grains. This anisotropy of the microstructure leads to anisotropy in dielectric, electrical and mechanical properties. In this study, grain oriented lanthanum titanate was produced by the sol–gel acrylamide polymerization route. The characterizations of the samples were achieved by thermal analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). X-ray diffraction indicates that the formation of monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} nanocrystals is a necessary first step to obtain orthorhombic LaTiO{sub 3} nanocomposites (with space group Pbnm). In this work we identified that the monoclinic perovskite La{sub 2}Ti{sub 2}O{sub 7} with space group P2{sub 1} transforms its structure into one with the orthorhombic space group Cmc2{sub 1} at approximately 1073 K. The microstructure associated consisted of flaky monoclinic La{sub 2}Ti{sub 2}O{sub 7} nanocomposites in comparison with round-shaped LaTiO{sub 3} nanocomposites. - Highlights: • The flaky-like La{sub 2}Ti{sub 2}O{sub 7} compound was synthesized by sol–gel acrylamide route. • Simultaneous monitoring of the DTA and XRD with temperature was performed. • Phase transformation characterization of La{sub 2}Ti{sub 2}O{sub 7} has been carried out. • The variation of the La{sub 2}Ti{sub 2}O{sub 7} and LaTiO{sub 3} grain morphology has been compared.