First total H ⁺/Li ⁺ Ion Exchange in Garnet-Type Li ₅La ₃Nb ₂O ₁₂ using organic acids and studies on the effect of Li stuffing

Garnet-type Li _5+xBa _xLa _3-xNb ₂O ₁₂ (x = 0, 0.5, 1) was prepared using a ceramic method, and H ⁺/Li ⁺ ion exchange was performed at room temperature using organic acids, such as CH ₃COOH and C ₆H ₅COOH, as proton sources. Thermogravimetric analysis showed that H ⁺/Li ⁺ ion exchange was nearly (100%) completed using the x = 0 member with CH ₃COOH, while it proceeded to about 40% for x = 0.5 and 13% for x = 1. In C ₆H ₅COOH, proton exchange proceeded to about 82% for x = 0, ∼40% for x = 0.5, and ∼25% for x = 1. Similar proton-exchange trends were reported in H ₂O, where ion exchange occurs more readily for garnets with lower Li content in Li _5+xBa _xLa _3-xNb ₂O ₁₂, that is, when excess Li ions preferentially reside in the tetrahedral sites of the garnet structure.