Influence of the Preparation Route on the Structural, Morphological and Spectroscopic Properties of SrTiO 3 and SrTiO 3
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INFLUENCE OF THE PREPARATION ROUTE ON THE STRUCTURAL, MORPHOLOGICAL AND SPECTROSCOPIC PROPERTIES OF SrTiO3 AND SrTiO3:Eu3+ POWDERS. Gisele Gasparotto1, Guilhermina F.Teixeira1, Marco A. Cebim1, José A.Varela1, Leinig A. Perazolli1 and Maria A. Zaghete1. 1
São Paulo State University, Chemistry Institute - UNESP, Araraquara, Brasil Rua Professor Francisco Degni -55- C. Postal 355, 14800-060- Araraquara, SP, Brasil ABSTRACT This research shows the influence of the synthesis route in the structural and morphological characteristics as well as in the luminescent properties of doped with europium and pure SrTiO3 (STO) powders prepared by microwave assisted hydrothermal synthesis, MWH, and by the polymeric precursor method, PPM. The XRD at room temperature of the STO powders nominally pure obtained by PPM at 700oC for 3 hours, as well as by the MWH at 190oC by 30 minutes present all the reflection peaks for the cubic perovskite structure (JCPDS-ICDD 35-734). The morphology varies according to the synthesis route. The particles of pure STO obtained by PPM presents morphology in the form of plates and the morphology of the particles synthesized by MWH is spherical with approximately 150 nm. The photoluminescent analysis shows for pure STO wide bands associated with the transition of charge transfer from the titanates group (TiO3)2- that are centered on 450 nm. In both preparation methods the emission bands obtained in the composites spectra were found to be asymmetric and low intense. However, in the case of the STO prepared by the PPM a bigger FWHM of the band can be observed. The excitation of the samples was done using a laser (Coherent Innova) with wavelength of 350 nm. INTRODUCTION Ferroelectric materials have been investigated for many years as a result of their excellent dielectric, piezoelectric as well as optoelectric properties [1,2]. The following materials can be found among the class of materials pertaining to the composites group of the Perovskits family (ABO3). The strontium titanate (STO) which can be classified as a semiconductor n-type with a energy bandgap about 3.2 eV can be mentioned once it presents a wide range of diversified applications such as gas sensors [3], solar cells [4], photo catalysts [5], photoelectrodes [6]. Over the last years, STO photoluminescence has become a field of study that has attracted immense attention in the area of material sciences as a result of the interesting effects that were discovered at room temperature [7, 8]. Lima and collaborators [9] have studied titanates ABO3 (A=Sr e Pb) structure in both disordered and ordered crystalline states and the results obtained by XANES for the disordered structure revealed the presence of two types of titanium coordination in ATiO3, clusters of pentacoordinated titanium TiO5 and clusters of hexacoordinated titanium TiO6. The photoluminescence in these composites is exactly related to the presence of these clusters and can be related to the transition of charge transfer O2---Ti4+, where an electron occupying an orbit of a non-ligand c
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