Enthalpy of Formation of Rare-earth Silicates Y2SiO5 and Yb2SiO5 and N-containing Silicate Y10(SiO4)6N2

1999 ◽  
Vol 14 (4) ◽  
pp. 1181-1185 ◽  
Author(s):  
Jian-Jie Liang ◽  
Alexandra Navrotsky ◽  
Thomas Ludwig ◽  
Hans J. Seifert ◽  
Fritz Aldinger
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Enthalpy Of Formation ◽  
Temperature Drop ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Binary Oxides ◽  
Standard Enthalpies Of Formation ◽  
Oxygen Gas ◽  
The Enthalpy Of Formation

The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.

Enthalpies of formation of LaBO3perovskites (B = Al, Ga, Sc, and In)

2003 ◽  
Vol 18 (10) ◽  
pp. 2501-2508 ◽  
Author(s):  
Jihong Cheng ◽  
Alexandra Navrotsky
Keyword(s):  
High Temperature ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Tolerance Factor ◽  
Enthalpies Of Formation ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
First Time ◽  
The Enthalpy Of Formation

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaBO3(B = La, Ga, Sc, and In). Enthalpies of formation from oxides of LaAlO3and LaGaO3are −69.61 ± 3.23 kJ/mol and −52.39 ± 1.99 kJ/mol, respectively. The data were consistent with literature values obtained using other methods. The enthalpies of formation of LaScO3and LaInO3from oxides were reported for the first time as −38.64 ± 2.30 kJ/mol and −23.99 ± 2.31 kJ/mol, respectively. As seen for other perovskites, as the tolerance factor deviates more from unity (in the order Al, Ga, Sc, In), the enthalpy of formation from oxides becomes less exothermic, indicating a less stable structure with respect to the constituent oxides.

Thermochemistry of Si6–zAlzOzN8–z(z = 0 to 3.6) materials

1999 ◽  
Vol 14 (12) ◽  
pp. 4630-4636 ◽  
Author(s):  
Jian-Jie Liang ◽  
Alexandra Navrotsky ◽  
Valerie J. Leppert ◽  
Michael J. Paskowitz ◽  
Subhash H. Risbud ◽  
...  
Keyword(s):  
Free Energy ◽  
High Temperature ◽  
Alkali Metal ◽  
Nitrogen Content ◽  
Configurational Entropy ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Accelerate Oxidation ◽  
Oxygen Gas ◽  
Metal Borate

Enthalpies of formation were determined for β-sialon phases (Si6–zAlzOzN8–z, z = 0.46 to 3.6) by high-temperature oxidative drop solution calorimetry using an alkali-metal borate (52 wt% LiBo2; 48 wt% NaBO2) solvent. Oxygen gas was bubbled through the melt to accelerate oxidation of the oxynitride samples during dissolution. Sialons near z = 2 appear less stable energetically than ones with higher or lower nitrogen content. A large configurational entropy contribution for sialons with z > 2 may further stabilize these materials. This larger free energy driving form may be the reason for success in pulse-activated processing of these materials. The enthalpies of formation further suggest that a greater driving form for oxynitride formation exists in batch synthesis using SiO2 rather than Al2O3.

Calorimetric determination of the enthalpy of formation of InN and comparison with AlN and GaN

2001 ◽  
Vol 16 (10) ◽  
pp. 2824-2831 ◽  
Author(s):  
M. R. Ranade ◽  
F. Tessier ◽  
A. Navrotsky ◽  
R. Marchand
Keyword(s):  
Enthalpy Of Formation ◽  
Standard Enthalpy ◽  
Sodium Molybdate ◽  
Solution Calorimetry ◽  
Large Error ◽  
Area Measurement ◽  
Enthalpies Of Formation ◽  
Standard Enthalpy Of Formation ◽  
Straight Line ◽  
The Enthalpy Of Formation

The standard enthalpy of formation of InN at 298 K has been determined using high-temperature oxidative drop solution calorimetry in a molten sodium molybdate solvent at 975 K. Calorimetric measurements were performed on six InN samples with varying nitrogen contents. The samples were characterized using x-ray diffraction, chemical analysis, electron microprobe analysis, and Brunauer–Emmett–Teller surface area measurement. The variation of the enthalpy of drop solution (kJ/g) with nitrogen content is approximately linear. The data, when extrapolated to stoichiometric InN, yield a standard enthalpy of formation from the elements of ?28.6 ± 9.2 kJ/mol. The relatively large error results from the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in good agreement with the old combustion calorimetric result by Hahn and Juza (1940). However, this calorimetric enthalpy of formation is significantly different from the enthalpy of formation values derived from the temperature dependence of the apparent decomposition pressure of nitrogen over InN. A literature survey of the enthalpies of formation of III–N nitride compounds is presented.

scholarly journals Natural kaersutite: ftir, raman, thermal and thermochemical investigations

2019 ◽  
Vol 64 (6) ◽  
pp. 651-657
Author(s):  
L. P. Ogorodova ◽  
Yu. D. Gritsenko ◽  
M. F. Vigasina ◽  
L. V. Melchakova
Keyword(s):  
High Temperature ◽  
Gibbs Energy ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Thermochemical Study ◽  
Calvet Microcalorimeter ◽  
Isomorphic Series ◽  
End Members ◽  
The Enthalpy Of Formation

A thermochemical study of the natural oxo-amphibole ─ kaersutite Na0.4K0.3(Ca1.6Na0.4)(Mg2.9Fe0.82+Al0.7Ti0.6Fe0.53+)[Si6.1Al1.9O22](OH)0.2O1.8.(alkaline basalts of Mongolia) was performed on a Tian-Calvet microcalorimeter. The enthalpy of formation from the elements ∆fH el0(298.15 K) = – 12102 ± 16 kJ/mol) was obtained by the method of high-temperature melt solution calorimetry. The entropy, enthalpy and Gibbs energy of the formation of the end-members of the isomorphic series kaersutite NaCa2Mg3TiAl[Si6Al2O22]O2 – ferri-kaersutite NaCa2Mg3TiFe3+[Si6Al2O22]O2 were estimated.

Thermochemische Untersuchungen zum ternären System Bi/Se/O. II. Das Teilsystem Bi2O3– SeO2/Thermochemical Investigations on the Ternary System Bi/Se/O.II.The Binary System Bi2O3–SeO2

1999 ◽  
Vol 54 (2) ◽  
pp. 239-251 ◽  
Author(s):  
H . Oppermann ◽  
H . Göbel ◽  
H . Schadow ◽  
P. Schmidt ◽  
C. Hennig ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Total Pressure ◽  
Room Temperature ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Standard Entropy ◽  
Pressure Measurements ◽  
Standard Enthalpies Of Formation ◽  
Higher Temperature ◽  
The Enthalpy Of Formation

We describe the existence of six thermodynamically stable phases on the binary line Bi2O3- SeO2 at room temperature: Bi12SeO20, Bi10Se2O19, Bi16Se5O34, Bi2SeO5, Bi2Se3O9 and Bi2Se4O11. At higher temperature we optained evidence for Bi20Se3O36 and Bi4SeO8. The decomposition pressures were measured for all phases in a membrane zero manometer and the enthalpy of formation and the standard entropy was determined. The phase barogram and phase diagram followed from total pressure measurements and differential thermoanalysis. The standard enthalpies of formation of all phases were also derived from solution calorimetry. The necessary data of transitions on molar enthalpies were obtained by DSC- and Cp-measurements.

Energetics of Manganese Oxides

1995 ◽  
Vol 398 ◽  
Author(s):  
S. Fritsch ◽  
A. Navrotsky
Keyword(s):  
Phase Diagram ◽  
High Temperature ◽  
Enthalpy Of Formation ◽  
Manganese Oxides ◽  
Temperature Drop ◽  
Solution Calorimetry ◽  
Drop Calorimetry ◽  
Thermodynamic Cycles

ABSTRACTThe energetics of some manganese oxides : pyrolusite ΜnO2, bixbyite Μn2O3, hausmannite Μn3O4 and manganosite MnO were studied by transposed temperature drop calorimetry and high temperature drop solution calorimetry in molten 2PbOB2O3 at 977 K. The enthalpies of oxidation at 298 K in the Mn-O system, determined by appropriate thermodynamic cycles, are (in kJ/mol O2) : −441.4 ± 5.8 for the reaction 6 MnO + O2 -> 2 Mn3O4, −201.8 ± 8.7 for 4 Mn3O4 + O2 -> 6 Mn2O3 and −162.1 ± 7.2 for 2 Mn2O3 + O2 -> 4 ΜnO2 These values agree very well with previous data obtained by equilibrium ρθ2 measurements and indicate that direct calorimetrie measurements are well suited to obtain reliable enthalpy of formation data for oxides containing manganese in the 2+, 3+ and 4+ states. The phase diagram of the Mn-O system was calculated using these new values of enthalpies.

Enthalpy of formation of cubic yttria-stabilized hafnia

2004 ◽  
Vol 19 (6) ◽  
pp. 1855-1861 ◽  
Author(s):  
Theresa A. Lee ◽  
Alexandra Navrotsky
Keyword(s):  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Fluorite Phase ◽  
Complex Solution ◽  
Calorimetric Data ◽  
Solution Theory ◽  
Anion Sublattice ◽  
Oxide Melt ◽  
The Enthalpy Of Formation

The enthalpy of formation of cubic yttria-stabilized hafnia from monoclinic hafnia and C-type yttria was measured by oxide melt solution calorimetry. The enthalpies of formation fit a function independent of temperature and quadratic in composition. The enthalpies of transition from m-HfO2 and C-type YO1.5, to the cubic fluorite phase are 32.5 ± 1.7 kJ/mol and 38.0 ± 13.4 kJ/mol, respectively. The interaction parameter in the fluorite phase is strongly negative, -155.2 ± 10.2 kJ/mol, suggesting even stronger short range order than in ZrO2–YO1.5. Regular solution theory or any other model assuming random mixing on the cation and /or anion sublattice is not physically reasonable. A more complex solution model should be developed to be consistent with the new calorimetric data and observed phase relations.

Thermodynamic properties of montechellite

2019 ◽  
Vol 64 (12) ◽  
pp. 1274-1280
Author(s):  
L. P. Ogorodova ◽  
Yu. D. Gritsenko ◽  
M. F. Vigasina ◽  
A. Yu. Bychkov ◽  
D. A. Ksenofontov ◽  
...  
Keyword(s):  
High Temperature ◽  
Gibbs Energy ◽  
Solution Calorimetry ◽  
Thermochemical Study ◽  
Gibbs Energy Of Formation ◽  
Calvet Microcalorimeter ◽  
Magnesium Orthosilicate ◽  
Calcium And Magnesium ◽  
The Enthalpy Of Formation ◽  
Energy Of Formation

A thermochemical study of natural calcium and magnesium orthosilicate ─ monticellite (Ca1.00Mg0.95)[SiO4] (Khabarovsk Territory, Russia) was carried out on the Tian-Calvet microcalorimeter. The enthalpy of formation from the elements fHоel(298.15 K) = -2238.4 4.5 kJ / mol was determined by the method of high-temperature melt solution calorimetry. The enthalpy and Gibbs energy of formation of monticellite of the theoretical composition of CaMg[SiO4] are calculated: fH0el(298.15 K) = -2248.4 4.5 kJ/mol and fG0el(298.15 K) = -2130.5 4.5 kJ/mol.

Sign in / Sign up

Export Citation Format

Share Document