Exploring the ‘consolidation factor’ in materials: impact on microstructures, phases and performances

Abstract

The contribution of different types of strains (e.g., lattice strain, thermal strain, doping-induced strain) in crystalline materials is well understood. In this article, we explain the effect of shaping-induced strain, which exists in a multi-dimensional shaped body (in contrast to its free powder form). We define this as the consolidation factor and illustrate its pivotal influence in the overall phase, composition and microstructural development of various ceramics and allied materials. The closest analogy of this effect could be related to the size-induced phase transformation in free powder systems. To validate the impact of the consolidation factor, two common heat treatments (i.e., sintering of compact powder and calcining the free powder of the same composition under the same sintering condition) have been carried out throughout the study. The findings establish the consolidation factor as a critical mechanism influencing phase stability, particularly in doped zirconia, where it restricts the formation of the deleterious monoclinic phase and stabilizes the tetragonal and cubic structures at low dopant concentrations. The influence of this factor was also validated in many other material systems, such as BaTiO₃, BaCO₃, and TiO₂. A comparative analysis between the sintered ceramics and calcined powders reveals that uniaxial compaction-induced stress fields modulate dopant distribution, grain boundary mobility, and phase transformation kinetics, impacting phase purity and grain growth behavior. In situ and ex situ XRD, Raman spectroscopy, and microstructural investigations confirm that the consolidation factor critically governs strain-mediated phase evolution, offering new insights into optimizing nanoceramic processing for enhanced functional and structural performance.