Chemical Transport of Solid Solutions. 8. Transport Phenomena and Ionic Conductivity in the In2O3/SnO2 System Chemical transport reactions are a suitable pathway to the preparation of In2O3‐rich and SnO2‐rich mixed crystals coexisting in the In2O3/SnO2 system (Cl2 as transport agent, 1050 → 900 °C). Experiments are consistent with thermodynamic calculations. The existence of other phases in the system In2O3/SnO2 could not be confirmed. The ionic conductivity of In2O3(SnO2) was investigated.