  Efficient synthesis recipes are needed both to streamline the manufacturing
of complex materials and to accelerate the realization of theoretically
predicted materials. Oftentimes the solid-state synthesis of multicomponent
oxides is impeded by undesired byproduct phases, which can kinetically trap
reactions in an incomplete non-equilibrium state. We present a thermodynamic
strategy to navigate high-dimensional phase diagrams in search of precursors
that circumvent low-energy competing byproducts, while maximizing the reaction
energy to drive fast phase transformation kinetics. Using a robotic inorganic
materials synthesis laboratory, we perform a large-scale experimental
validation of our precursor selection principles. For a set of 35 target
quaternary oxides with chemistries representative of intercalation battery
cathodes and solid-state electrolytes, we perform 224 reactions spanning 27
elements with 28 unique precursors. Our predicted precursors frequently yield
target materials with higher phase purity than when starting from traditional
precursors. Robotic laboratories offer an exciting new platform for data-driven
experimental science, from which we can develop new insights into materials
synthesis for both robot and human chemists.
