Fabricating a layer including lithium lanthanum zirconate (Li7La3Zr2O12) layer includes forming a slurry including lanthanum zirconate (La2Zr2O7) nanocrystals, a lithium precursor, and a lanthanum precursor in stoichiometric amounts to yield a dispersion including lithium, lanthanum, and zirconium. In some cases, the dispersion includes lithium, lanthanum, and zirconium in a molar ratio of 7:3:2. In certain cases, the slurry includes excess lithium. The slurry is dispensed onto a substrate and dried. The dried slurry is calcined to yield the layer including lithium lanthanum zirconate.