Charge attachment induced transport times two - sequential double-CAIT in Li₃B₇O₁₂

Area of Science:

• Materials Science
• Solid-State Chemistry
• Ion Transport Phenomena

Background:

• Charge Attachment Induced Transport (CAIT) is a technique to study ion mobility in materials.
• Understanding ion diffusion is crucial for developing advanced materials for energy storage and electronics.

Purpose of the Study:

• To investigate sequential ion exchange in Li3B7O12 glass using a Double-CAIT approach.
• To determine the concentration dependence of diffusion coefficients for Li+ and Rb+ ions.
• To probe the energy landscape of both native and ion-exchanged glass using foreign ions.

Main Methods:

• Performed two consecutive CAIT experiments on Li3B7O12 glass: Rb+@Li3B7O12 followed by Cs+@Rb+@Li3B7O12.
• Measured concentration depth profiles using secondary ion mass spectrometry (SIMS).
• Quantitatively simulated depth profiles using Nernst-Planck-Poisson (NPP) theory.

Main Results:

• The second CAIT experiment (Cs+) demonstrated the ability to displace previously exchanged Rb+ and native Li+ ions deeper into the glass.
• Derived diffusion coefficients for Li+ and Rb+, revealing concentration dependence, particularly for Li+ in both experiments and Rb+ in the second.
• Observed that Rb+ diffusion was concentration-independent in the first CAIT but dependent in the second.

Conclusions:

• The study confirms the CAIT principle of foreign ions probing the material's energy landscape, even after ion exchange.
• Results suggest that thermal equilibrium may not be achieved after the first CAIT experiment.
• Intricate ion-ion interactions were identified, linked to similarities in bulk diffusion coefficients.