Microstructural Evolution During Crystallization of Ba₅Nb₄O₁₅ from Ba-Nb Ethoxide

Abstract

Ba₅Nb₄O₁₅ was successfully crystallized from Ba5-Nb4 ethoxide by heating. Microstructual characterization of specimens annealed at various temperatures was performed by using a transmission electron microscope (TEM). Below 673 K, the ethoxide was decomposed to an amorphous matrix. At 773 K, small crystals with a size of 2-3 nm formed in the amorphous phase. The crystal was grown by heating, and then Ba₅Nb₄O₁₅ crystals 70-150 nm in size formed at 1173 K. The crystallization process was successfully observed in situ by TEM using a thermal specimen stage. The grain growth process from polycrystal to five single crystals could be recorded. We propose a formation mechanism of Ba₅Nb₄O₁₅ from Ba₅-Nb₄ ethoxide.