Thermochromic Solid-Solid Phase Transition δ-CsPbI3 → α-CsPbI3 Studied by Differential Scanning Calorimetry and Direct Visual Observation-An Undergraduate Physical Chemistry Lab Experiment

Thermochromism is a fascinating phenomenon in which a material undergoes a color change with a change in the temperature. This undergraduate lab experiment explores the thermodynamics of the thermochromic solid-solid phase transition of CsPbI3 from the delta (orthorhombic, yellow) to the alpha (cubic, black) phase using differential scanning calorimetry. Use of an innovative DSC instrument allows the direct observation of the sample's color change during the experiment. With the data obtained from the DSC measurements, the students write a laboratory report that includes a brief description of the experimental procedure, an account of their visual observation, and the calculation of the values of Delta H degrees and Delta S degrees for the phase transition with their respective uncertainties. Details of the activity, i.e., procedure, experimental data acquisition, and analysis, are provided.