Effect of precursory solution anion and non-stoichiometry on the properties of yttrium gadolinium iron garnet

Experimental data for the Y_2.01 Gd_0.99Fe₅O₁₂ system indicates that addition of sulphate anion to the Fe(NO₃)₃ solutions increases sintered density of the garnet made by spray drying precursory solutions followed by rotary calcining. A smaller particle size and a higher green density of calcined powders obtained from solutions with sulphate added, provide a higher sinterability compared to the powders obtained from nitrate solutions. Conventional ball-milling of calcined powders is eliminated. Sintered density of more than 99% theoretical can be obtained. Data for the Y_2.01(1–x) Gd_0.99(1–x) Fe_5(1–y)O₁₂ system indicates that a second phase of (Y, Gd) FeO₃ decreases the sintered density of iron deficient garnet. A second phase of (Y, Gd) FeO₃ also accounts for lower dielectric loss tangent for these compositions.