MULTI STAGE SHRINKING CORE MODEL FOR PHASE CONVERSION TOWARDS YTTRIUM IRON GARNET

• Main Author: Anthoni Stanpo, Vito
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66377
• Institution: Institut Teknologi Bandung

Yttrium Iron Garnet (YIG) is a soft ferrite commonly used for the high-frequency circulator.YIG usually is made through CSSR (Conventional Solid State Route) methods. Despite its merits, this process requires high energy and intermediary phase YIP (Yttrium Iron Perovskite) presence during its manufacture. In addition, the formation and controlling mechanism for YIG phase conversion hasn't yielded any conclusive results. This study aims to get a better understanding of the YIG phase conversion mechanism and how temperature and excess Fe2O3 affect YIG formation. Series of simulation is carried out by utilizing the shrinking core model to predict YIG phase conversion. Later, the experiment consists of powder preparations, compaction, sintering, and XRD phase characterization. Varying excess Fe2O3 by x (x = 0%, 5%, 10%, and 15%) and sintering temperature (1273 K and 1473 K) had been done to observe changes in YIG formation. Based on this study, YIG formed through intermediary phase YIP that further react forming YIG. In the range of 1273-1523 K, the controlling mechanism in YIG phase conversion is mixed controlled consists of diffusion and chemical reaction phenomenon which has the highest R2 value among proposed models. The effective diffusion coefficient and reaction rate constant follow ln De = -34411 T-1 -11.213 and ln kv = -34589 T-1 + 18.032 with De in m2s-1 and kv in s-1 respectively. Increasing both temperature and excess Fe2O3 promotes YIG formation. It is found there is a solubility limit of 10% excess Fe2O3, where a higher value of excess Fe2O3 will be resulting in the hematite phase in the sample.