TY - JOUR
T1 - Thermodynamics of ZnxMn3-xO4 and Mg1-zCuzCr2O4 spinel solid solutions
AU - Lilova, Kristina
AU - Sharma, Geetu
AU - Hayun, Shmuel
AU - Shoemaker, Daniel P.
AU - Navrotsky, Alexandra
N1 - Funding Information:
Financial support from DOE Grant DE-FG02-97ER1 is gratefully acknowledged. The authors thank Dr. Ram Seshadri (University of California, Santa Barbara) for his valuable contribution and support.
Publisher Copyright:
Copyright © 2019 Materials Research Society.
PY - 2019/10/14
Y1 - 2019/10/14
N2 - The thermodynamic properties of ZnxMn3-xO4 and Mg1-zCuzCr2O4 spinel solid solutions have been studied using high-temperature oxide melt solution calorimetry. Except for MgCr2O4 spinel, which possesses cubic structure, the other three end-members are tetragonal. The enthalpies of mixing are small endothermic and fit subregular solution behavior. The main contribution to the energetics of mixing of both spinel systems comes from the difference in the crystal structure between the end-members: a change in the tetragonal distortion for ZnxMn3-xO4 solid solutions and a transition from cubic to tetragonal for the Mg1-zCuzCr2O4 system. If all Mg1-zCuzCr2O4 spinels possessed the same structure, the mixing enthalpies would be close to zero. Because both series have normal cation distributions, the entropies of mixing are equal to the configurational entropies of mixing of Zn2+ and Mn2+ and of Mg2+ and Cu2+ on tetrahedral sites, and the activities would follow Raoult's law. The calculated Gibbs energy of mixing confirms the absence of solvus at any temperature for both systems.
AB - The thermodynamic properties of ZnxMn3-xO4 and Mg1-zCuzCr2O4 spinel solid solutions have been studied using high-temperature oxide melt solution calorimetry. Except for MgCr2O4 spinel, which possesses cubic structure, the other three end-members are tetragonal. The enthalpies of mixing are small endothermic and fit subregular solution behavior. The main contribution to the energetics of mixing of both spinel systems comes from the difference in the crystal structure between the end-members: a change in the tetragonal distortion for ZnxMn3-xO4 solid solutions and a transition from cubic to tetragonal for the Mg1-zCuzCr2O4 system. If all Mg1-zCuzCr2O4 spinels possessed the same structure, the mixing enthalpies would be close to zero. Because both series have normal cation distributions, the entropies of mixing are equal to the configurational entropies of mixing of Zn2+ and Mn2+ and of Mg2+ and Cu2+ on tetrahedral sites, and the activities would follow Raoult's law. The calculated Gibbs energy of mixing confirms the absence of solvus at any temperature for both systems.
KW - calorimetry
KW - crystallographic structure
KW - geologic
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U2 - 10.1557/jmr.2019.196
DO - 10.1557/jmr.2019.196
M3 - Article
AN - SCOPUS:85067514110
VL - 34
SP - 3305
EP - 3311
JO - Journal of Materials Research
JF - Journal of Materials Research
SN - 0884-2914
IS - 19
ER -