25th anniversary article: metal oxide particles in materials science: addressing all length scales

The fundamental mission of materials science is the description of matter over all length scales. In this review, we apply this concept to particle research. Based on metal oxides, we show that every size range offers its specific features, and every size range had its era, when it was in the center of the research activities. In the first part of the review, we discuss on three metal oxides as examples, how and why the research focus changed its targeted size regime from the micrometer to the nanometer scale and back to the macroscopic world. Next, we present the distinct advantages of using nanoparticles over micrometer-sized particles in selected devices and we point out how such a shift in the size regime opens up new research directions. Finally, we exemplify the methods to introduce nanoparticles into macroscopic objects to make functional ceramics.