Low‐Temperature Chemical Synthesis of Lanthanum Monoaluminate

Abstract

One of the promising candidates for ferroelectric substrate materials, lanthanum monoaluminate (LaAlO3), was successfully synthesized by two separate chemical powder preparation techniques: (i) homogeneous precipitation from aqueous solutions containing urea (CH4N2O) in the presence of nitrate salts, and (ii) self‐propagating combustion synthesis from aqueous solutions containing CH4N2O and the respective nitrate salts of lanthanum and aluminum. The submicrometer, spherical‐like particles of the precursors were completely converted to pure LaAlO3 at 850C in the homogeneous precipitation route, and the same conversion temperature was observed to be 750C, which becomes the lowest temperature ever reported for the powder synthesis of a pure LaAlO3 phase. The materials were characterized by powder X‐ray diffractometry, simultaneous thermogravimetric/differential thermal analysis, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. Structural refinements by Rietveld analysis showed that LaAlO3 was isostructural with BaTbO3 and had the space group R‐3c, in contrast to the previously assumed space group of R‐3m for this phase. The atomic positions in the structure of LaAlO3 were refined and presented for the first time, with respect to the present space group.