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 degrees C, 1210-1285 degrees C, and 1190-1255 degrees 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 degrees C, and 1275 and 1380 degrees 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.