Kinetics and Mechanism of Formation of Barium Zirconate from Barium Carbonate and Zirconia Powders

Abstract

The formation of BaZrO 3 from very fine (70–90 nm) ZrO 2 powders and coarser (∼1 μm) BaCO 3 powders has been studied in dry and humid air up to 1300°C using TGA/DTA, XRD, SEM, TEM, and EDS microanalysis. In the temperature range 900°–1100°C, barium is rapidly transported at the surface of the ZrO 2 particles and reacts, forming BaZrO 3 . The compound grows as a concentric layer with gradual consumption of the central ZrO 2 particle. The overall formation kinetics of BaZrO 3 is well described by a diminishing core model, and the most likely rate‐determining step is a phase‐boundary process at the ZrO 2 –BaZrO 3 moving interface. The size and shape of the final particles is generally determined by the morphology of the starting ZrO 2 particles and not by that of the BaCO 3 . The reaction is faster in humid air than in dry air, and the activation energy decreases from 294 kJ·mol −1 (dry air) to 220 kJ·mol −1 (humid air). When the fraction reacted is >80–90 mol%, the reaction rate rapidly decreases.