A flame spray pyrolysis method for making nanoscale, lithium ion-conductive ceramic powders comprises providing a precursor solution comprising chemical precursors dissolved in an organic solvent, and spraying the precursor solution into an oxidizing flame to form a nanoscale, lithium ion-conductive ceramic powder, wherein a concentration of the chemical precursors in the solvent ranges from 1 to 20 M. The precursor solution can comprise 1-20% excess lithium with respect to a stoichiometric composition of the ceramic powder. Nominal compositions of the nanoscale, ceramic powders are Li1.4Al0.4M1.6(PO4)3 where M is Ti or Ge.