  The numerous stories around LK-99 as a possible room-temperature
superconductor over the summer of 2023 epitomise that materials are more than a
bulk crystallographic structure or an expected composition. Like all materials,
those at the core of technologies for the energy generation transition,
including batteries, catalysts or quantum materials draw their properties from
a hierarchy of microstructural features where impurities can dramatically
influence the outcomes. As we move towards a circular economy, the recycling of
materials will inevitably create fluxes of increasingly impure materials,
generating new challenges for fabricating materials with controlled properties.
Here, we provide our perspective on how high-end microscopy and microanalysis
have helped us to understand relationships between synthesis, processing and
microstructure, avoiding imprecise or even erroneous interpretations on the
origins of the properties from a range of materials. We highlight examples of
how unexpected impurities and their spatial distribution on the nanoscale can
be turned into an advantage to define pathways for synthesis of materials with
new and novel sets of physical properties.
