New Topotactic Derivatives of the Open-Framework Semiconductor KBi ₃ S ₅ via a Low-Temperature Solid-State Ion-Exchange Route

A new low-temperature solid-state ion-exchange route has been used to ion-exchange KBi ₃ S ₅ . The new method allows the solid-solid ion-exchange of the K ⁺ ions for the smaller cations Li ⁺ and Na ⁺ , as well as for the NH ⁺ ₄ at the remarkably low temperature regime of 110-130°C. The topotactically ion-exchanged seriesA _x K _1-x Bi ₃ S ₅ (A=Li, Na, and NH ₄ ) was prepared and characterized by powder X-ray diffraction, differential scanning calorimetry, differential thermal analysis, thermal gravimetric analysis, semiquantitative microprobe analyses, solid-state UV/vis/near-IR spectroscopy, and variable-temperature solid-state ⁷ Li NMR spectroscopy.