The bottom-up approach describes the synthesis of bulk materials from the finest possible length scales to obtain the best global properties. This approach was adapted to the synthesis of multi-phase ceramic composites produced from metal oxides produced by liquid-feed flame spray pyrolysis (LF-FSP). The effect of length scale of mixing was tested through two processing schemes, mixed single metal-oxide nanopowders (NPs) and nanocomposite NPs having the desired composition within single particles. For the Al2O3-Y2O3-ZrO2 ternary system, composites prepared from nanostructured nanoparticles sinter to finer grain sizes (<410nm) at equivalent densities of 95%TD than those prepared from mixed nanoparticle processing. These contrast with our previous studies in this area where mixed NP processing gave the best or equivalent results. The nanocomposite NPs produced in this study exhibit novel nanostructures with three phases contained within single particles <26nm average particle size (APS). This nanostructure may directly explain the enhanced sintering of the nanocomposite NPs and may provide an impetus for future synthesis of similarly structured NPs.