Critical nuclei size effect in the densification of nanostructured niobia ceramics

An effective technique for obtaining near-theoretical density niobium oxide by utilizing the critical nuclei size effect is reported. Dense nanostructured niobium oxide with more than 99% of the theoretical maximum and an average grain size of less than 90 nm was produced by sintering during a metastable-to-stable phase transformation at 650°C. The tendency of the particulate system to reach the critical nuclei size by reducing the surface energy through the replacement of solid–gas interface by solid–solid interface (densification process) is one of the main reasons for this excellent sintering behavior.