Phase stability of SrZnxFe(2−x)Fe16O27 (0.0 ≤ x ≤ 1.0) in low oxygen pressures

Abstract

The phase stability of Zn-substituted strontium W-type hexaferrites (SrZnxFe(2-x)Fe16O27; SrZnxFe(2-x)W) in the low oxygen pressure (PO2) of 10−3 atm, and strontium W-type hexaferrite (SrFe18O27; SrW) in the PO2 region of 10−3–10−2 atm were systemically investigated. For this study, polycrystalline samples were sintered at high temperatures in low PO2 and then furnace-cooled. Analyses of the phases and microstructures of sintered samples revealed that the SrZnxFe(2-x)W phases are thermodynamically stable at the temperature regions of 1245–1320 °C, 1210–1285 °C, and 1190–1255 °C, for x = 0.0, 0.5, and 1.0, respectively in the PO2 of 10−3 atm. In addition, the SrW phase was found to be stable at the temperature region between 1245 and 1320 °C, and 1275 and 1380 °C in the PO2 of 10−3 and 10−2 atm, respectively, which enabled the construction of stability phase diagram of SrW on the PO2 versus 10 000/T (K) plot in the PO2 region of 10−3 to 0.21 atm.