Kinetic study of α-BZN crystallization obtained from chemical method

Materials Research

Ronaldo Rodrigues Pelá²  Luciana Simone Cividanes²  Deborah Dibbern Brunelli²  Sonia Maria Zanetti¹  Gilmar Patrocinio Thim² 

[1] ,Instituto Tecnológico de Aeronáutica Departamento de Química São José dos Campos SP ,Brazil

关键词: BZN;    pyrochlore;    Avrami;    kinetic;   

DOI  :  10.1590/S1516-14392008000300010

来源: SciELO

【 摘 要 】

The crystallization kinetics of ceramics composed by Bi2O3-ZnO-Nb2O5 (BZN) was studied using non-isothermal method. The BZN samples were prepared by the polymeric precursors method. Phase evolution was evaluated by X ray diffraction and the thermal events were evaluated by differential scanning calorimetry (DSC). The crystallization of BZN occurs from 500 to 700 °C, which corresponds to a secondary event in DSC curves. The principal exothermic event in these curves is related to the decomposition of organic material and was isolated from the crystallization peak by deconvolution into two Gaussian curves. Those related to crystallization processes were evaluated in terms of crystallized fraction. Kinetic parameters were determined from Ligero (E = 242 ± 7) kJ.mol-1 and Kissinger (E = 241 ± 24) kJ.mol-1 methodologies and they are very close. The activation energy Ea = (241 ± 24) kJ.mol-1 and (242 ± 7) kJ.mol-1 (by the Kissinger and Ligero methodology, respectively), frequency factor k0 =10(13).s-1 and exponent of Avrami n = (1.3 ± 0.1) were determined. The n value indicates that the crystallization is diffusion controlled, with decreasing nucleation rate. Scanning electronic microscopy showed the presence of nanoparticulated powder.

【 授权许可】

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