Preparation of textured bismuth titanate ceramics through templated grain growth combined with spark plasma sintering

Textured bismuth titanate (Bi ₄Ti ₃O ₁₂), the simplest and best known compound among the bismuth layer-structure ferroelectrics is interesting because of its peculiar switching behavior which results from a small c-axis component of the spontaneous polarization and a small coercive force. We prepared Bi ₄Ti ₃O ₁₂ ceramics through the templated grain growth (TGG) method combined with the spark plasma sintering (SPS) method. The TGG method was developed to provide a simpler way of creating textured ceramic microstructures. The SPS method enables a compact powder to be sintered under uniform heating to a high density at relative low temperatures and with much shorter sintering periods than with conventional sintering. We obtained a Bi ₄Ti ₃O ₁₂ precursor powder through a co-precipitation method with Ti alkoxide and Bi oxide as raw materials. Platelet Bi ₄Ti ₃O ₁₂: was synthesized from the precursor powder through a flux method using NaCl and KCl. The obtained platelet Bi ₄Ti ₃O ₁₂ had a high aspect ratio. The ceramics were prepared by SPS treatment using a mixture of the platelet Bi ₄Ti ₃O ₁₂ and the amorphous precursor powder. As a result, dense ceramics could be easily obtained without crystalline amorphous precursors and grain growth was not observed during the sintering. After heat treatment of the ceramics, we obtained highly textured, high density Bi ₄Ti ₃O ₁₂ ceramics. The ceramics showed high orientation, above 70%, for the c-axis direction and high density of over 85%.