Co 3O 4-Co 2ZnO 4 spinels: The case for a solid solution

摘要: Abstract In prior first-principles theoretical work we predicted a complete solid solution in the Co3O4–Co2ZnO4 system, with negligibly small mixing enthalpy. this tested prediction on bulk, large-grained specimens across join, combining oxide melt calorimetry, differential scanning precise lattice parameter measurements, anomalous X-ray and neutron diffraction, situ electrical measurements. The calorimetric results confirm presence of at high temperatures, but large enthalpy that exceeds value. Because Co3O4 Co2ZnO4 have essentially identical parameters, energetic destabilization must arise from factors other than strain energy resulting size mismatch. Changes Co3+ spin states vs. temperature zinc content are proposed to account for positive excess enthalpy, may also provide additional entropy stabilize temperature.