Tunable thermal expansion in framework materials through redox intercalation

The control of thermal expansion is important for practical applications but very difficult to achieve. Here we show that redox intercalation allows to control thermal expansion from negative to zero to positive by insertion of Li ions into the simple negative thermal expansion (NTE) material ScF3. The small concentration of intercalated Li ions has a strong influence on the transverse vibrations of fluorine atoms, which are responsible for NTE. Redox intercalation of guest ions is thus likely to be a general and effective method for tailoring thermal expansion in NTE framework materials.