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Gadolinium-iron ferrites: composition and structure
(EN)
Spyrellis, N
(EN)
Tsagaroyannis, J
(EN)
Loizos, Z
(EN)
Haralambous, KJ
(EN)
The composition and structure of some mixed gadolinium-iron oxides has been investigated in relation to their preparation conditions. Gadolinium ferrites were prepared by employing a wet chemical method. Different ratios of gadolinium to iron oxides were used and the formation of the ferrites was studied over a temperature range of 700-1500-degrees-C. Specifically, pure gadolinium and iron oxides as well as hydrated mixed oxides with a Gd:Fe atom ratio of 1:1, 3:5 and 2:1 were fired at designated temperatures up to 1480-degrees-C in air and inert argon atmospheres. The firing procedure was followed by subsequent quenching at room temperature, in order that the ferrites would maintain the composition and structure attained at the higher temperature. The changes in composition and structure of the ferrites, taking place as a function of temperature, firing atmosphere, and initial oxide composition used, were investigated by thermal analysis, X-my diffraction and Mossbauer spectra. It is shown that the ferrite composition and structure depend on the Gd : Fe atom ratio and the preparation conditions. Above 1400-degrees-C, the mixtures of a 1:1 Gd:Fe atomic ratio tend to form the perovskite (orthoferrite) phase (GdFeO3), whilst the 3: 5 mixtures form the garnet phase (Gd3Fe5O12). On the other hand, 2:1 mixtures contain the perovskite and gadolinium oxide phases at the same elevated temperatures.
(EN)
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