Thermochemistry of tantalum(V) bromide

1979 ◽  
Vol 57 (19) ◽  
pp. 2665-2668 ◽  
Author(s):  
Alan D. Westland
Keyword(s):  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Heat Capacities ◽  
Gaseous Compound ◽  
The Enthalpy Of Formation

The enthalpy of formation of crystalline TaBr5 is found by solution calorimetry to be −142.9 ± 0.4 kcal mol−1. Estimates of entropies and heat capacities lead to thermochemical quantities for the liquid and gaseous compound as well.

Silicon nitride: Enthalpy of formation of the α- and β-polymorphs and the effect of C and O impurities

1999 ◽  
Vol 14 (5) ◽  
pp. 1959-1968 ◽  
Author(s):  
Jian-jie Liang ◽  
Letitia Topor ◽  
Alexandra Navrotsky ◽  
Mamoru Mitomo
Keyword(s):  
Solid Solution ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Molar Enthalpy ◽  
Solid Solution Series ◽  
Solution Series ◽  
Α Phase ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
The Enthalpy Of Formation

High-temperature oxidative drop solution calorimetry was used to measure the enthalpy of formation of α− and β−Si3N4. Two different solvents, molten alkali borate (48 wt% LiBO2 · 52 wt% NaBO2) at 1043 and 1073 K and potassium vanadate (K2O · 3V2O5) at 973 K, were used, giving the same results. Pure α− and β−Si3N4 polymorphs have the same molar enthalpy of formation at 298 K of −850.9 ± 22.4 and −852.0 ± 8.7 kJ/mol, respectively. The unit cell dimensions of impure α−Si3N4 samples depend linearly on the O and C impurity contents, and so does the molar enthalpy of formation. The energetic stability of the α−Si3N4phase decreases when the sample contains O and C impurities. The experimental evidence strongly suggests that the impurities dissolve into the α−Si3N4 structure to form a (limited) isostructural solid solution series but that this solid solution series is energetically less stable than a mechanical mixture of pure (α or β) Si3N4, SiO2, and SiC. Thus, the α-phase is not stabilized by impurities and is probably always metastable.

Thermochemistry of lanthanum zirconate pyrochlore

2009 ◽  
Vol 24 (11) ◽  
pp. 3350-3357 ◽  
Author(s):  
A.V. Radha ◽  
Sergey V. Ushakov ◽  
Alexandra Navrotsky
Keyword(s):  
Melting Point ◽  
Enthalpy Of Formation ◽  
Sodium Molybdate ◽  
Solution Calorimetry ◽  
Standard Enthalpy Of Formation ◽  
Lanthanum Zirconate ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
The Enthalpy Of Formation

A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ∼33–35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0f,ox, for stoichiometric lanthanum zirconate pyrochlore is −107.3 ± 5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is −4102.2 ± 6.0 kJ/mol. La2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ∼350 kJ/mol, respectively.

Determination of the Enthalpy of Formation of SmOCl by Solution Calorimetry

ChemInform ◽  
2003 ◽  
Vol 34 (18) ◽  
Author(s):  
Heinrich Oppermann ◽  
Peer Schmidt ◽  
Dao Quoc Huong ◽  
Claudia Hennig
Keyword(s):  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
The Enthalpy Of Formation

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.

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.

scholarly journals Thermochemistry of the lower bromides of tantalum

1980 ◽  
Vol 58 (9) ◽  
pp. 938-941 ◽  
Author(s):  
Alan D. Westland
Keyword(s):  
Enthalpy Of Formation ◽  
Standard Enthalpy ◽  
Solution Calorimetry ◽  
Heat Capacities ◽  
Enthalpies Of Formation ◽  
Standard Enthalpy Of Formation

The standard enthalpy of formation of tantalum(IV) bromide has been determined by solution calorimetry: ΔHf0(TaBr4(c) 298 K) = −125.6 ± 0.5 kcal mol−1. Experimental estimates of the enthalpies of formation of tantalum(III) bromide and tantalum(II,III) bromide were also obtained. Estimates of the entropies and heat capacities of the compounds are also given.

Energetics of cubic Si3N4

2006 ◽  
Vol 21 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Yahong Zhang ◽  
Alexandra Navrotsky ◽  
Toshimori Sekine
Keyword(s):  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Standard Enthalpy Of Formation ◽  
Calorimetric Measurement ◽  
Synthesis Conditions ◽  
Oxide Melt ◽  
Equilibrium Reactions ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
The Enthalpy Of Formation

High-temperature oxide melt drop solution calorimetry was used to study the energetics of formation of cubic silicon nitride prepared at high pressure. The standard enthalpy of formation of c-Si3N4 is −776.3 ± 9.5 kJ/mol. The calorimetric measurement of Si3N4 in 3Na2O·4MoO3 solvent was validated by comparing the enthalpy of formation for β–Si3N4 with previous work using alkali borate solvent. The enthalpy of transformation from β– to c-Si3N4 is 80.2 ± 9.6 kJ/mol. This value appears consistent with the observed synthesis conditions, which do not represent reversed equilibrium reactions.

Enthalpy of formation of the cubic fluorite phase in the ceria–zirconia system

2008 ◽  
Vol 23 (4) ◽  
pp. 1105-1112 ◽  
Author(s):  
Theresa A. Lee ◽  
Christopher R. Stanek ◽  
Kenneth J. McClellan ◽  
Jeremy N. Mitchell ◽  
Alexandra Navrotsky
Keyword(s):  
Enthalpy Of Formation ◽  
Solid Solutions ◽  
Regular Solution Model ◽  
Solution Calorimetry ◽  
Fluorite Phase ◽  
Oxygen Sublattice ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
The Enthalpy Of Formation

The enthalpy of formation of cubic ceria–zirconia solid solutions (c-Ce(1−x)ZrxO2, 0.05 ⩽ x ⩽ 0.75) at 25 °C with respect to monoclinic zirconia (m-ZrO2) and cubic ceria (c-CeO2) has been measured by high-temperature oxide melt solution calorimetry. In contrast to fluorite solid solutions containing trivalent oxides (e.g., yttria–zirconia), mixing in c-Ce1−xZrxO2 shows moderate positive deviation from ideality. Evaluating the data within the framework of a regular solution model, the interaction parameter, Ω, is +51.0 ± 8.0 kJ/mol. The introduction of undersized Zr into CeO2 severely distorts and destabilizes the oxygen sublattice. Destabilization of c-Ce1−xZrxO2 may be relieved by reduction or clustering. A stable ordered compound in the CeO2–ZrO2 system is thermodynamically unlikely.

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