Impedance analysis of CaZrO3 samples synthesized by microwave-assisted hydrothermal method

Reference Presenter Authors
08-064 Wagner Dias Macedo Junior Junior, W.D.(Universidade Estadual Paulista); Souza, A.E.(Universidade Estadual Paulista); Teixeira, S.R.(Universidade Estadual Paulista); Longo, E.(INSTITUTO DE QUÍMICA - UNESP); Sakamoto, W.K.(Universidade Estadual Paulista); Calcium Zirconate (CZO) is an important ceramic of the perovskite family, which has been the subject of research in several areas, aiming at a variety of applications such as moisture sensors, catalysts in the photodegradation of dyes harmful to the environment and host matrix for the insertion of photoluminescent species such as Eu3+. Alternative routes for the synthesis of this material are extremely important because they allow the creation of new structures, morphologies and physical characteristics. In this work, CZO at nanoscale was synthesized for the first time using the microwave-assisted hydrothermal method (MAH) where there was a subsequent thermal treatment for the crystallization of the obtained phases, this method allows obtaining homogeneous samples with a short time of synthesis. Samples at 1, 10, 40 and 180 min were synthesized using the MAH method, which were then treated in an oven at 1200 ºC. It was found that, prior to the heat treatment, the samples have not yet fully crystallized, which is indicated by the existence of three broad bands in the X-ray diffraction spectrum. After the heat treatment, all samples crystallize completely and have two distinct phases: Orthorhombic CaZrO3 orthorhombic and cubic Ca0.16Zr0.86O1.87 . Both phases, after heat treatment, have an average crystallite size ranging from 55 to 68 nm. Through the Cole-Cole plot it is possible to observe that the radius of the semicircles decrease according to the increase of the synthesis time, this is indicative of the influence of this time in the morphology of the material, because the larger the radius of the semicircle, the higher the resistance values, which is generally related to a more disorganized material with larger defects and grain boundaries. Of course, the capacitance of these materials also varied with the time of synthesis: at the working frequency of 1 kHz, the values of 5.96 to 4.58 pF were recorded for the samples synthesized at 1 to 180 min respectively.
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