| Abstract
| - Solid-state reactions between metal sulfates and metal oxides (assisted by K2CO3) havebeen used to prepare two classes of important perovskite materials: ferroelectric PbTiO3and the catalyst/magnetic/fuel-cell material La1-xSrxMnO3 (x = 0.0 and 0.3). K2CO3 helps todrive the reaction by forming highly stable K2SO4 and CO2. Performing the reactions withinsolid monoliths and then dissolving out K2SO4 crystals in water permit macroporous materialsto be obtained. The monoliths possess connected, open porosity with characteristic pore sizesof the order of 5−30 μm. Imprinted on this macroporous structure is a second, smaller scaleof porosity arising from the sintering together of particles with sizes in the 100−300-nmrange. The reaction pathways have been followed by thermodiffractometry, and the productscharacterized by Rietveld refinement of powder X-ray diffraction patterns, by scanningelectron microscopy, and by dc magnetization measurements.
- Assisted metathesis reactions between suitable solid precursors, carried out in pressed pellets, yield intimate mixtures of a functional perovskite material and a second, water-soluble phase as products. Removing the second phase in water permits a macroporous monolith of the functional material (magnetic La0.7Sr0.3MnO3 in the figure) to be obtained.
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