Disclosed herein are garnet material compositions, e.g., lithium-stuffed garnets and lithium-stuffed garnets doped with alumina, which are suitable for use as electrolytes and catholytes in solid state battery applications. Also disclosed herein are lithium-stuffed garnet thin films having fine grains therein. Also disclosed herein are methods of making and using lithium-stuffed garnets as catholytes, electrolytes and/or anolytes for all solid state lithium rechargeable batteries. Also disclosed herein are electrochemical devices which incorporate these garnet catholytes, electrolytes and/or anolytes. Also disclosed herein are methods for preparing dense thin (