Effects of Burial Powder Configuration on the Microstructure, Composition, and Ion Conductivity of Perovskite Li _{3 x} La _{1/3‐ x} TaO ₃ Ion Conductors

Abstract A combustion synthesis methodology for the preparation of perovskite Li 3 x La 1/3‐ x TaO 3 lithium‐ion conductors with x = 0.033 is presented. Bulk ceramic specimens were sintered under combinations of burial powder and cover crucibles to provide different lithium vapor overpressure conditions. A maximum total lithium ion conductivity of 6 × 10 ‐6 S cm ‐1 at room temperature was found for the pellet covered by a crucible whose lip was sealed using parent powder (moderate overpressure), with agreement to the maximum in the intergranular ion conductivity. Intragranular conductivity was maximized at the low overpressure condition. The trend in ion conductivity was found to correspond to the lithium content in the samples through a combination nuclear reaction analysis and energy dispersive X‐ray spectroscopy phase constitution measurements. The mechanism impacting ion conductivity was determined to be changes in the amount of LaTaO 4 secondary phase as driven by the processing conditions during sintering.