Please use this identifier to cite or link to this item: http://cimav.repositorioinstitucional.mx/jspui/handle/1004/1272
MICROSTRUCTURE AND CHEMICAL COMPOSITION EVOLUTION IN Ba0.9Ca0.1Ti0.9Zr0.1O3 COMPOUND PREPARED BY PECHINI METHOD
Guillermo Manuel Herrera Perez
ARMANDO REYES ROJAS
LUIS EDMUNDO FUENTES COBAS
OSCAR OMAR SOLIS CANTO
CARLOS ELIAS ORNELAS GUTIERREZ
Acceso Abierto
Sin Derechos Reservados
Microstructure
The development of lead free materials such as Ba0.9Ca0.1Ti0.9Zr0.1O3, (BCZT) to preserve the environmental protection is a scientific challenge [1]. Technological aspects are also interesting when an appropriate selection of their stoichiometry is chosen; this material could be to stay near to called morphotropic boundary phase [2]. This phase is important due to BCZT shows a high piezoelectric coefficient [3]. The aim of this work is to prepare the perovskite BCZT by Pechini polymeric precursor method, monitoring the microstructure and chemical composition evolution. Two important process were considered in the synthesis; the chelation process where cations were chelated with ethylenediaminetetraacetic acid and citric acid; and the polymerization process where ethylene-glycol was incorporated to the solution. A gel was obtained and dried at 60 oC during 12 h. The resulting material was analyzed by X-ray diffraction (XRD) and the amorphous phase was confirmed (Fig. 1a). This precursor was heated at 700 oC during 1h in order to stabilize the tetragonal crystal phase (PDF 05-0626) with P4mm symmetry. The XRD pattern was refined by Rietveld method using Fullprof software (Fig. 1b) in order to elucidate the crystal parameters. The atomic force microscopy (AFM, MFP-3D Infinity) image (Fig. 1c) shows a homogeneity of particles size. These particles also shows a homogeneous round shape distribution. The surface has a root-mean-square roughness of 5.2 nm. Figure 2a shows the particle morphology of BCZT powders heat-treated at 700 oC obtained by transmission electron microscopy (TEM-Philips CM 200) during 1h. The analysis shows large pieces of agglomerated particles with average diameter of 18.3 ± 1.4 nm. One can observe also homogeneous polygon-shape particles. The elemental analysis in TEM-electron energy loss spectroscopy (EELS) mode were performed through the Zr M2,3-edge, Ca L2,3-edge, Ti L2,3 edge, O K-edge and Ba M4,5-edge (Fig. 2b). In order to study the possibility of a lowered oxidation state for Ti ions atomic multiplet theory including the crystal field was employed. The calculation shows the presence of only one oxidation state Ti4+ L2,3 in Oh symmetry with a crystal-field splitting about 2.15 eV. The Field Emission Scanning Electron Microscopy (FESEM, JSM-7401F) image of the heat-treated sample is shown in Fig. 3a, which indicates well-developed grains in the compound. The average grain size was determined with the help of image J and it found to be
2015
Memoria de congreso
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