TY - JOUR
T1 - Thermodynamic relations among olivine, spinel, and phenacite structures in silicates and germanates. IV. The system ZnOMgOGeO2
AU - Navrotsky, A.
N1 - Funding Information:
thoseb elow 900°Cw ered one hydrothermally Acknowledgments at 0.5k bar waterp ressureF. or this discussion This work was supported by the National Science wes halln eglectth es malle ffecot f thed ifference Foundation (Grants GP-20402 and GH-39767). The in pressureo n the phased iagram. germaniumd ioxide used was donatedb y the Sylvania As seenf rom Fig. 2, at low temperatures, Corporation. C. Heilman and D. S. Kenny assistedi n only one spine1p hasei s formed; that is the the experimentalw ork. one derived from Mg,GeO, by zinc sub- stitution. There is no evidencef or a second spine1n ear Xzn20e0=, 0.5, such as is formed in the analogousc obalt and nickel systems. The reasonf or this differenceis not known. References The substitutiono f zinc into the spine1p hase 1. A. NAVROTSKY, J. Solid State Chem.6 ,21 (1973). permits the retentiono f a stability field for 2. A. NAVROTSKY, J. Solid State Chem.6 ,42 (1973). that structureu p to about8 8O”C,a sc ompared 3. A. NAVROTSKY, J. Solid State Chem.1 1, 10 (1974). to 810°C for the olivine-spine1t ransition 4. F. DACHILLE AND R. ROY, Amer. J. Sci. 258, 225 in Mg,GeO, (4). This would suggeste ither (1960). that Zn,GeO, spine1is somewhamt ores table J. F. SARVER AND F. A, HUMMEL, J. Amer. Ceram. than Zn,GeO, olivine (which our data at E. R. SEGNIT AND A, E. HOLLAND, J. Amer. Ceram. Sot. 45, 304( 1962);a nd 48,411 (1965). 1200°Cd o not seemt o support)o r that the Sot. 48,412(1965). spine1p haseso f intermediatceo mpositiona re Y. SYONO, S. AKIMOTO, stabilized, such as by additional configur-Chem.3 ,369 (1971). ational disorderi nvolving Zn, Mg, and Ge, 0. S. KENNY AND A. NAVROTSKY, relativet o Zn-substitutedo livines. Chem.3 4,2115( 1972).
Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 1975/1/1
Y1 - 1975/1/1
N2 - Phase relations in the system ZnOMgOGeO2 were determined at 1200°C in air. Subsolidus phase relations along the pseudobinary join Zn2GeO4Mg2GeO4 were determined between 700 and 1200°C, the portion below 900°C was obtained hydrothermally. Only one spinel phase is formed at low temperatures; this phase extends from Mg2GeO4 to (Mg0.73Zn0.27)2GeO4 at 820°C. Its highest temperature of stability is 880°C, with a composition of (Mg0.75Zn0.25)2GeO4. The free energies of transformation from the olivine to the phenacite structures at 1200°C are estimated to be + 6 ± 1.0 kcal/mole and - 10 ± 1.5 kcal/mole for Mg2GeO4 and Zn2GeO4, respectively.
AB - Phase relations in the system ZnOMgOGeO2 were determined at 1200°C in air. Subsolidus phase relations along the pseudobinary join Zn2GeO4Mg2GeO4 were determined between 700 and 1200°C, the portion below 900°C was obtained hydrothermally. Only one spinel phase is formed at low temperatures; this phase extends from Mg2GeO4 to (Mg0.73Zn0.27)2GeO4 at 820°C. Its highest temperature of stability is 880°C, with a composition of (Mg0.75Zn0.25)2GeO4. The free energies of transformation from the olivine to the phenacite structures at 1200°C are estimated to be + 6 ± 1.0 kcal/mole and - 10 ± 1.5 kcal/mole for Mg2GeO4 and Zn2GeO4, respectively.
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U2 - 10.1016/0022-4596(75)90173-5
DO - 10.1016/0022-4596(75)90173-5
M3 - Article
AN - SCOPUS:49549138971
SN - 0022-4596
VL - 12
SP - 12
EP - 15
JO - Journal of Solid State Chemistry
JF - Journal of Solid State Chemistry
IS - 1-2
ER -