Solid state precursors Synthesis of Magnetic Garnets a Crystalline, phase-pure material Magnetic garnets(tunable magnetic materials) aqueous m Great for spinels, e.g., chromite Y(NO) 3+Gd(NO)+FeCl+NaOH-Y Gda FesO, a Chromite Spinel Precursor NH2Mg(CO少26H2O1150°C Firing at 900"C, 18-24 hrs, pellets, regrinding, repelletizing peated firings, removes RFeO, perovskite impurity CNH2NCrO2·6HO somorphous replacement of Y* for Gd*on dodecahedral MnCr o MnCr O2“5CH2N 1100°C ites, solid solution, similar rare earth ionic radii CoCr O, CoCr,. 5C,HN 1200°C Cucr.O (NH)Cu(CrO去2·2NH 750°C loda, 2Fe+ occupied in On sites, 3Fe+Ta sites, 3RE+ ZnCrO (NH),Zn(CrO ), 2NH, 1400C ight for rmula units in a unit cell of 160 atoms. cubic lattice unit, cell parameter follows Gda- FesO1g)=Px3(Y3 O1g)+P(3-x/3(Gd, FesO12) Synthesis of Magnetic Garnets Coprecipitation Technique Coprecipitation applicable to nitrates, acetates, aAny property(P)of a solid-solution member is the atom oxalates. alkoxide and so forth weighted average of the end-members ole magnetic properties by tuning the x value Requires: try garnet Y Gda-yFesO12 . Y GdrxFe, O creates a tunable magnetic garnet that is strongly temperature and composition dependent asimilar precipitation rates applications in permanent magnets, magnetic recording "no supersaturation media, magnetic bubble memories and so forth, similar Useful for spinels and the like concepts apply to magnetic spinels Disadvantage: difficult to prepare high purity, Combinatorial Materials Chemistry- Self Propagating High Temperature Robots Can Do Solid State Synthesis! Combinatorial materials chemistry, the wave of the Synthesis (SHS) Used for parallel synthesi of compounds, rapid eXtreme exothermicity of a reaction can be used to ts, clever analytical provide high temperatures needed for diffusion plied to high Te superconductors, inorganic phosphors, tHermite Fe.0.+Al>ALO. +Fe has been used to ake a number of useful materials including fractory ceramic parts that can be pressed and machined to final size8 Solid State Precursors Crystalline, phase-pure material Decomposes on heating Great for spinels, e.g., chromite spinels Chromite Spinel Precursor Ignition(°C) MgCr2O4 (NH4 )2Mg(CrO4 )2•6H2O 1150°C NiCr2O4 (NH4 )2Ni(CrO4 )2•6H2O 1100°C MnCr2O4 MnCr2O7•5C5H5N 1100°C CoCr2O4 CoCr2O7•5C5H5N 1200°C CuCr2O4 (NH4 )2Cu(CrO4 )2•2NH3 750°C ZnCr2O4 (NH4 )2Zn(CrO 4 )2•2NH3 1400°C Magnetic garnets(tunable magnetic materials) aqueous precursor technique: Y(NO3 ) 3+Gd(NO3 ) 3+FeCl3+NaOH®YxGd3-xFe5O12 Firing at 900°C, 18-24 hrs., pellets, regrinding, repelletizing, repeated firings, removes RFeO3 perovskite impurity Isomorphous replacement of Y3+ for Gd3+ on dodecahedral sites, solid solution, similar rare earth ionic radii: 0<x<3, 2Fe3+ occupied in Oh sites, 3Fe3+ Td sites, 3RE3+ dodecahedral sites eight formula units in a unit cell, total of 160 atoms, cubic lattice unit, cell parameter follows Vegard’s law behavior: P(YxGd3-xFe5O12)=Px/3(Y3Fe5O12)+P(3-x)/3(Gd3Fe5O12) Synthesis of Magnetic Garnets Any property (P) of a solid-solution member is the atom fraction weighted average of the end-members Tunable magnetic properties by tuning the x value in the binary garnet YxGd3-xFe5O12 YxGd3-xFe5O12 creates a tunable magnetic garnet that is strongly temperature and composition dependent, applications in permanent magnets, magnetic recording media, magnetic bubble memories and so forth, similar concepts apply to magnetic spinels Synthesis of Magnetic Garnets Coprecipitation applicable to nitrates, acetates, oxalates, alkoxides, and so forth Requires: ßsimilar salt solubilities ßsimilar precipitation rates ßno supersaturation ßUseful for spinels and the like Disadvantage: difficult to prepare high purity, accurate stoichiometric phases Coprecipitation Technique Combinatorial Materials Chemistry¾¾ Robots Can Do Solid State Synthesis! Combinatorial materials chemistry, the wave of the future, beware traditional solid state chemists! Used for parallel synthesis of series of compounds, rapid screening by parallel measurements, clever analytical techniques, massive amounts of data . Applied to high Tc superconductors, inorganic phosphors, giant magnetoresistant (GMR) mixed valency perovskites, high dielectric constant rutile type oxides, mixed metal catalysts and electrocatalysts, and even hydrothermal synthesis of zeolites. Self Propagating High Temperature Synthesis (SHS) Extreme exothermicity of a reaction can be used to provide high temperatures needed for diffusion Thermite Fe2O3 + Al ® Al2O3 +Fe has been used to make a number of useful materials including refractory ceramic parts that can be pressed and machined to final size