ORDENAMENTO EM PEROVSQUITAS COMPLEXAS

Abstract

In the present work, it was developed the synthesis and properties of complex perovskites with general formula Ba3MNb2O9, where M = Ca (BCN) e Zn (BZN), in the form of ceramics powders, sintered pellets, and thin films by Pechini methed. The key point od study incorporated the observation of the formation of ordered and partially ordered perovskite phase like 1:2 form by measuring the X-ray diffraction and Raman spectroscopy of the systems under study. It was discussed briefly the general properties and structural aspects in simple and complex perovskites, the latter emphasizing the importance of the ordered phase in phycal properties. The phenomenological theory of Landau was employed in understanding the dynamics of order-disorder transition in convergent and non converget cátion ordering. The probing of the kinetics of crystallization of the BCN and BZN ceramic powders was made reaching the formation of partially ordered phase impurities free at 900°C/2h with average particle size estimated at 100nm. By adjusting the collected spectra, we werw able to correlate both the position and width of the band near to 800 cm-1 with annealing temperature from A1g stretching mode behavior. It was showed the formation of partially ordered phase os BCN pellets sinterd at 160°C/2h, whose order parameter estimated by the Raman spectra approached 0,97. Moreover, the order parameter as estimated by X-ray diffraction reached 0,50 in the BZN sintered pellets by high temperature ceramic method. Finally, the batium niobate imourity was mapped on the surface of the BZN thin films using Raman maps in the x-y plane. Measurements revealed that Raman depth in such films have thicknesses between 1,7µm and 2,1µm.