Magnetic property enhancement through microstructural engineering and phase purity control of ceramic materials
The effects of powder synthesis and processing on the magnetic properties of the high power microwave ceramic yttrium iron garnet ( Y3Fe5O12) and the high temperature superconductor YBa2Cu3O7- x (123) were studied. Yttrium iron garnet was produced through a thermal decomposition technique. It was found that the use of iron sulfate over iron citrate in the stock solution resulted in phase pure Y3Fe5O12 at the relatively low temperature of 1100oC with a short soak time of four hours. The low forming temperature resulted in fine-grained powder that was easily milled. Milled powder was hot forged at 1275oC for 1.5 hours resulting in a 96% dense sample with an average grain size of 1.7 ± 0.6 μm. These samples were found to have a higher critical magnetic field than those presently commercially available; 211 Oe compared to 162 Oe, while not affecting the dielectric or magnetic characteristics. YBa2Cu3O7-x and Y2BaCuO5 (211) were prepared using a combustion synthesis technique. Phase pure 123 and 211 were formed by calcining combusted powder at 900oC for 4 hours and 930oC for 3 hours respectively. Tape casting and lamination were used to form bulk samples of pure 123 sheets and 123 alternated with mixed oxide and combustion synthesized 211 sheets. After melt texturing, the alternating layer structures were found to have a wider magnetization curve, a higher critical current density, a lower degree of liquid egress and a greater resistance to corrosion than either 123 only pellets or laminates.
- Pub Date:
- Engineering: Materials Science, Physics: Electricity and Magnetism