Abstract
Yttrium iron garnet was obtained using four methods of synthesis. A modified citrate method and a modified citrate method with YIG (yttrium iron garnet, Y3Fe5O12) nucleation were used. In two subsequent methods, YIP (yttrium iron perovskite, YFeO3) and α-Fe2O3 obtained in the first case by the citrate method and in the second by precipitation of precursors with an ammonia solution were used as the input precursors for reaction sintering. Differential scanning calorimetry (DSC) measurements of the output powders obtained by all methods allowed to identify the effects observed during the temperature increase. Dilatometric measurements allowed to determine the changes in linear dimensions at individual stages of reaction sintering. In the case of materials obtained by the citrate method, two effects occur with the increasing temperature, the first of which corresponds to the reaction of the formation of yttrium iron perovskite (YIP), and the second is responsible for the reaction of the garnet (YIG) formation. However, in the case of heat treatment of the mixture of YIP and α-Fe2O3, we observe only the effect responsible for the solid state reaction leading to the formation of yttrium iron garnet. The obtained materials were reaction sintered at temperatures of 1300 and 1400 °C. Only in the case of material obtained from a mixture of perovskite and iron(III) oxide obtained by ammonia precipitation at temperature of 1400 °C were densities achieved higher than 98% of the theoretical density. The use of Hot Isostatic Pressing (HIP) in the case of this material allowed to eliminate the remaining porosity and to obtain full density.
Highlights
Yttrium iron garnet (Y3 Fe5 O12 ) is one of the more important materials with ferromagnetic properties
The traditional method of obtaining YIG from a mixture of yttrium oxide and iron oxide is based on a solid state reaction. Heating such a mixture at temperature of about 1300 ◦ C leads to the formation of yttrium iron garnet
Der and the Hot Isostatic Pressing (HIP) process was performed at 1400 °C for 2 h under 200 MPa and temperature rate of 10 °C/min
Summary
Yttrium iron garnet (Y3 Fe5 O12 ) is one of the more important materials with ferromagnetic properties It can be the base material for applications as an amplifier in microwave devices, circulator, insulator, phase shifter, etc. The traditional method of obtaining YIG from a mixture of yttrium oxide and iron oxide is based on a solid state reaction. Heating such a mixture at temperature of about 1300 ◦ C leads to the formation of yttrium iron garnet. In this method, it is very difficult to achieve an ideal homogenization of the system. As a result of roasting at high temperatures, there is significant grain growth and the formation of mechanically durable agglomerates [13,14]
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