Reviewing the cases of Nanoscale Heterogeneity in Ceramics: Boon or Bane?

Abstract

Size-dependent properties and their enormity of change make the whole domain of nanoscale materials exciting like anything; the fact that such property changes can be achieved with very small fractions of nanomaterials also helps the issue further. The same fact, however, is not so straightforward when it comes to ceramic materials. Ceramic phases changing their stabilities at the nanoscale and ceramic processing being known for complex high temperature operations – are the two key reasons why nanoceramic sector could not always deliver the results in an expected way. Whether it is the unexpected phase, microstructure or local compositional fluctuation/s – all can make a ceramic system heterogeneous at nanoscale. The important objective, however, remains to identify them (i.e., heterogeneities), understand them (i.e., reason/s behind their genesis) and use them (if possible) to advantage. In this review, numerous case studies on the factors influencing the nanoscale heterogeneities in ceramics have been presented. The role of raw materials, their synthesis, and processing factors have been emphasized along with the capability and limitation of conventional analytical tools in examining such complexities. Impacts on selected properties (i.e., as barrier or boon) have been discussed in connection to these heterogeneities. The case studies on nano-heterogeneities have been presented in a non-judgemental way so as to illustrate their impacts in both ways (i.e., either as a barrier or boon). Since heterogeneities in nano-ceramics have not been studied methodically (unlike polymers or metals) over the past, this article is expected to provide a background for starting the same.