Structural characterization of nanopowders of semiconductor ferroelectric oxides

Abstract

This research project approaches the structural characterization of nanopowders of ferroelectric oxides accompanied of structural refinement from X-ray diffraction date based on the Rietveld method. Furthermore, the consolidation and enhancement of a set of research lines of the Laboratory of Composites and Functional Ceramics (LaCCeF) should be reached. In this sense, four research lines implemented in the LaCCeF, involving the preparation and characterization of nanometric and nanostructured particles will be directly benefited. In addition, a new research line termed of Nanoscale Effect, in which both the electric and dielectric properties of nanoparticle and nanostructured one are investigated will also undergo a positive impact. Materials of interest belong to the kind of lead free ferroelectric termed of Tetragonal Tungsten Bronze (TTB) family, which exhibits potential application in technologic areas as linear dielectric and ferroelectric. In this project, TTB host structures Sr2NaNb5O15 and K2NdNb5O15, as well as its solid solutions with transition metal will be prepared using three chemical synthesis methods, as follow: Modified Poliol method, Combustion method, Polymeric Precursors method (Pechini). Classical oxide preparation route based on the conventional mechanical mixture of oxides/carbonates, using high efficiency milling process, an operational processing technique of Laboratory of Composites and Functional Ceramics (LaCCeF - FAPESP), DFQB/FCT/ UNESP will be also used. Both host structures Sr2NaNb5O15 and K2NdNb5O15 will compose with KSr2Nb5O15 and Sr3SnNb4O15, actually under investigation in the LaCCeF, a wide base of crystalline structures with distincts forms of occupation of specific sites. The process of optimization of parameters time and calcination temperatures, which are necessaries to the preparation of nanoparticle and nanostructured one of Sr2NaNb5O15, K2NdNb5O15 and its single phase solid solutions will be monitored by infrared spectroscopy, surface area (BET) measurement, thermal analysis (DSC e TGA) and luminescence spectroscopy. The Rietveld method, FULLPROF program, will be used to attain the profile of adjusting of the set of diffraction lines and refinement of the structural parameters, as atomic positions. From crystallographic parameters, the tridimensional representation of unitary cellule of above mentioned compounds will be constructed, using the CaRIne Crystallography 3.1®, CaRIne Crystallography 3.1®sr e CaRIne Crystallography 4.0® software. These softwares and the Jade 8 Plus software package will be used to the indexation of the diffraction pattern. All 4 softwares were acquired by research funding supported by CNPq - Process 47.4627/2004-7. (AU)