Jadwiga Brzezińska-Miecznik

Barium zirconate ceramic powder synthesis by the coprecipitation–calcination technique

The coprecipitation technique was used to prepare an intimate mixture of barium carbonate and hydrous zirconia gel. A part of barium ions became incorporated in the zirconia gel structure. Heat treatment of the system results in the crystallisation of the BaO in ZrO2 solid solution of tetragonal symmetry. The solid solution, when heated without contact with BaCO3, decomposes at elevated temperatures. It results in the formation of BaZrO3 and monoclinic zirconia solid solution. No solid solution of monoclinic symmetry appears when barium carbonate is present in the system. In this case, the reaction of the tetragonal solid solution with BaCO3 leads to the synthesis of BaZrO3. The highest sintering ability is observed in the powder, a small part of which remains unreacted.

YAG Powder Synthesis and Characteristics

Two techniques were applied to prepare single phase YAG powder: i) citrate process based on complexing properties of citric acid with isopropyl alcohol additive as esterification agent and ii) co-precipitation from relative nitrates solution with ammonia. At low temperature heat treatment both techniques lead to the X-ray amorphous bodies. Their calcination at elevated temperatures results in single-phase YAG powder. Differences in the behaviour of the amorphous precursors during heat treatment will be shown.