Preparation of Na0.5Bi0.5TiO3 ceramics by hydrothermal-assisted cold sintering

A recently proposed novel technique, termed "cold sintering process" (CSP), can provide dense ceramic solids at remarkably low temperatures around 180 degrees C. In a recent work, we successfully obtained dense Na0.5Bi0.5TiO3 ceramics by this method. Bismuth titanate sodium nanoparticles were prepared as the raw material powder by the hydrothermal synthesis route. A hydrothermal precursor solution was used as the transient solvent for cold sintering. Under the combined action of pressure and temperature, the Na0.5Bi0.5TiO3 green body was densified by dissolution-precipitation, and a preliminary densified ceramic sheet was obtained. The amorphous phase in the ceramic sheet was then transformed into a crystalline phase by annealing. Finally, densified Na0.5Bi0.5TiO3 ceramic sheets were obtained, with density of up to 99%, relative permittivity of 681, and dielectric loss of 0.08 at 10 kHz and room temperature. The piezoelectric coefficient d(33) of the sample was 52.5 pC/N. The properties of the prepared ceramics were comparable to those of the conventional sintered ceramics.