Performance improvement of S-band phase shifter using Al, Mn and Gd doped Y3Fe5O12 and sintering optimization

The searching for Y3Fe5O12 (YIG) ferrite base material is a difficult challenge for microwave phase shifter. Although YIG ferrite is promising for its good microwave characteristics, the adjustment of its corresponding magnetic properties for applied frequency is always a tough challenge. In this work, a study was made to evaluate the impacts of stoichiometry and sintering temperature on hysteresis properties of Mn, Al and Gd substituted YIG ferrites. The Mn, Al substituted YIG ferrite, (Y3)(MnxAl0.83−xFe4.17)O12 showed its best properties for application in 2-4 GHz frequency range (i.e. S-band) latching phase shifter at x = 0.13. Magnetic properties were further improved by sintering optimization. The increasing sintering temperature increases saturation magnetization (4πMs), remanence (Br) and squareness ratio (SQR), while decreasing the coercivity (Hc). To further investigate the impact to sintering process, Gd substituted YIG ferrites are also discussed. (Y3−yGdy)(Mn0.13Al0.7−0.5yFe4.17)O12 with y = 0.6 demonstrated its best magnetic properties at 1450 °C sintering. Although the 4πMs, Br and SQR are comparable to that of previous results, its Hc cannot meet the requirement. (Y3)(MnxAl0.83−xFe4.17)O12 ferrites with x = 0.13 sintered at 1430 °C shows the optimum magnetic properties: 4πMs = 675 G, Br = 575 G, Hc = 0.45 Oe, SQR = 0.86. Good ferromagnetic resonance (FMR) linewidth (i.e. ΔH) were also realized as 38.6 Oe at 3.2 GHz. Base on above results, we reveal Mn, Al substituted YIG ferrite is a good candidate for practical latch phase shifter applications at S-band.