Influence of ammonia on properties of nanocrystalline barium titanate particles prepared by a hydrothermal method

Abstract

The influence of ammonia on BaTiO3 particles prepared via hydrothermal synthesis is discussed. Two kinds of Ti-precursors, amorphous (with ammonia) and anatase (without ammonia), are synthesized by a hydrolysis reaction using Ti-butoxide as the starting material. Amorphous Ti-precursors are found to be excellent for this purpose and offer several advantages over anatase. Superior tetragonal properties of BaTiO3 powders with more uniform particle sizes can be achieved at 200 degrees C after 24 h using amorphous Ti-precursors. X-ray photoelectron spectroscopy was carried out on both types of Ti-precursor, and a decrease in H2O adsorption on the amorphous Ti-precursors is confirmed. It is considered that the reduction in H2O adsorption on the Ti-precursors results from the shielding effects of ammonia and is attributed to a decreased formation of intragranular pores in the BaTiO3 particles. These suggested mechanisms are clarified by the results of in situ transmission electron microscopy observations and density measurements of the hydrothermally synthesized BaTiO3.