Non-isothermal crystallization kinetics of the heavy-group lanthanide dititanates
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AuthorsMilićević, Bojana R.
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The systematic investigation of crystallization kinetics of heavy-group lanthanide dititanate pyrochlores, HL2Ti2O7 (HL=Lu, Tm, Er, Ho, Y, Dy, and Tb) is presented. Materials are prepared by the Pechini-type polymerized complex route, and their thermal properties were studied by differential thermal analysis under non-isothermal conditions. For this group, the crystallization temperature became larger with increasing the ionic radius of lanthanides, from 1066 K for Lu2Ti2O7 to 1125 K for Tb2Ti2O7. The linear dependence of crystallization temperature on radius of heavy lanthanide ions is found to follows T-c [K] = 168.86 + 920.89 x r(ion) [angstrom] semi-empirical equation. Apparent activation energies of crystallization were obtained from calculations based on the Arrhenius equation, isoconversional method and PerezMaqueda method, and are similar to 805 kJ mol(-1) calculated by three different methods. The crystallization kinetics followed the so-called Avrami Erofeev (A3) model, as co...nfirmed using several criteria, namely, the Malek, master plot, and Perez-Maqueda methods. The crystallization mechanism of all lanthanide dititanate pyrochlores is found to be the same, and the crystallization process involves a constant rate of nucleation and two-dimensional growth of nuclei. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:Lanthanide pyrochlores / Lanthanide dititanate / Thermal properties / Activation energy / Crystallization
Source:Optical Materials, 2017, 74, 86-92
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