Set forth 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 set forth herein are lithium-stuffed garnet thin films having fine grains therein. Disclosed herein are novel and inventive 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 novel electrochemical devices which incorporate these garnet catholytes, electrolytes and/or anolytes. Also set forth herein are methods for preparing novel structures, including dense thin (<；50um) free standing membranes of an ionically conducting material for use as a catholyte, electrolyte, and, or, anolyte, in an electrochemical device, a battery component (positive or negative electrode materials), or a complete solid state electrochemical energy storage device. Also, the methods set forth herein disclose novel sintering techniques, e.g., for heating and/or field assisted (FAST) sintering, for solid state energy storage devices and the components thereof.L'invention concerne des compositions de matériau de grenat, par exemple des grenats bourrés de lithium et des grenats bourrés de lithium dopés avec de l'alumine qui conviennent pour être utilisées comme électrolytes et catholytes dans des applications de batterie à électrolyte solide. L'invention concerne également de minces films de grenat bourré de lithium qui contiennent des grains fins. L'invention concerne des procédés nouveaux et inventifs permettant de fabriquer et d'utiliser des grenats bourrés de lithium comme catholytes, électrolytes et/ou anolytes pour toutes les batteries rechargeables au lithium à électrolyte solide. L'invention concerne également de nouveaux dispositifs électrochimiques qui incorporent ces catholytes, électrolytes et/ou anolytes en grenat. De même, l'invention
