Surface modification of BaTiO3 with catechol surfactant and effects on cold sintering

Abstract

The sintering of functionalized particles is an approach often used to obtain high performance functional ceramics. When molecular surfactants are used to functionalize particles, conventional sintering cannot be applied due to extremely high processing temperatures. Here, BaTiO₃ particles are grafted with different coverages using a catechol (CA) surfactant, and then these particles are densified under cold sintering with a (BaOH₂)⋅8H₂O transient flux. The adsorption of CA is equilibrated with various concentrations on BaTiO₃ particles at room temperature. The modeling (Langmuir and Freundlich adsorption) and the quantification (UV–vis absorption and thermogravimetric analysis) of CA coverage enable us to rigorously determine the degree of functionalization and conduct thorough cold sintering kinetics investigations as a function of CA coverage using a dilatometer. Microstructure is observed with electron microscopy techniques to determine the grain and grain boundary interfaces that result with the competition of surfactant coverage and densification driven by the dissolution and reprecipitation processes at the interfaces. A mechanism with the retardation of cold sintering kinetics is discussed based on these experimental observations.