Thermochemistry of Rare Earth Perovskites

MRS Advances ◽  
2016 ◽  
Vol 1 (38) ◽  
pp. 2695-2700 ◽  
Author(s):  
Dawei Feng ◽  
Alexandra Navrotsky
Keyword(s):  
Rare Earth ◽  
Solid Solutions ◽  
Solution Calorimetry ◽  
Sodium Content ◽  
Enthalpies Of Formation ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
Image Position ◽  
Light Rare Earth Elements

AbstractThe rare earth (RE) mineral loparite with the chemical composition (RE, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3 is the principal ore of the light rare earth elements (LREE) as well as niobium and tantalum. The enthalpies of formation of RE0.67-xNa3xTiO3 (RE = La, Ce) and Ca1-2xNaxLaxTiO3 from oxides and elements of lanthanum and cerium perovskites and their solid solutions have been obtained using high temperature oxide melt solution calorimetry. RE0.67-xNa3xTiO3 (RE = La, Ce) perovskites become more stable relative to oxide components as sodium content increases. Na0.5Ce0.5TiO3 and Na0.5La0.5TiO3 can be considered stable endmembers in natural loparite minerals. For perovskite solid solutions Ca1-2xNaxLaxTiO3, the enthalpies of formation from the constituent oxides $\Delta {\rm{H}}_{{\rm{f}},\,{\rm{ox}}}^^\circ$ become more exothermic with increasing Na+La content, suggesting a stabilizing effect of the substitution 2Ca2+ → Na+ + La3+ on the perovskite structure. The trend of increasing thermodynamic stability with decreasing structural distortion is similar to that seen in many other ABO3 perovskites.

scholarly journals Thermodynamics of Molybdenum Trioxide (MoO3) Encapsulated in Zeolite Y

2021 ◽  
Author(s):  
Xianghui Zhang ◽  
Andrew Strzelecki ◽  
Cody Cockreham ◽  
Vitaliy Goncharov ◽  
Houqian Li ◽  
...  
Keyword(s):  
Molybdenum Trioxide ◽  
Zeolite Y ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Metal Species ◽  
Enthalpies Of Formation ◽  
Host Interactions ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide

Zeolites with encapsulated transition metal species are extensively applied in the chemical industry as heterogenous catalysts for favorable kinetic pathways. To elucidate the energetic insights into formation of subnano-sized molybdenum trioxide (MoO) encapsulated/confined in zeolite Y (FAU) from constituent oxides, we performed a systematic experimental thermodynamic study using high temperature oxide melt solution calorimetry as the major tool. Specifically, the formation enthalpy of each MoO/FAU is less endothermic than corresponding zeolite Y, suggesting enhanced thermodynamic stability. As Si/Al ratio increases, the enthalpies of formation of MoO/FAU with identical loading (5 Mo-wt%) tend to be less endothermic, ranging from 61.1 ± 1.8 (Si/Al = 2.9) to 32.8 ± 1.4 kJ/mol TO (Si/Al = 45.6). Coupled with spectroscopic, structural and morphological characterizations, we revealed intricate energetics of MoO – zeolite Y guest – host interactions likely determined by the subtle redox and/or phase evolutions of encapsulated MoO.

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.

scholarly journals Enthalpies of formation of lanthanide oxyapatite phases

2001 ◽  
Vol 16 (10) ◽  
pp. 2780-2783 ◽  
Author(s):  
A. S. Risbud ◽  
K. B. Helean ◽  
M. C. Wilding ◽  
P. Lu ◽  
A. Navrotsky
Keyword(s):  
Structural Formula ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Enthalpies Of Solution ◽  
Thermodynamic Cycles ◽  
Oxide Melt ◽  
Formation Enthalpies ◽  
High Temperature Oxide ◽  
Standard Enthalpies Of Formation ◽  
Temperature Oxide

A family of lanthanide silicates adopts an oxyapatitelike structure with structural formula Ln9.33 0.67(SiO4)6O2 (Ln = La, Sm, Nd, Gd,   = vacancy). The enthalpies of solution, ΔHS, for these materials and their corresponding binary oxides were determined by high-temperature oxide melt solution calorimetry using molten 2PbO B2O3 at 1078 K. These data were used to complete thermodynamic cycles to calculate enthalpies of formation from the oxides, ΔH0 f-oxides (kJ/mol): La9.33 0.67(SiO4)6O2 = 776.3 ± 17.9, Nd9.33 0.67(SiO4)6O2 = 760.4 ± 31.9, Sm9.33 0.67(SiO4)6O2 = 590.3 ± 18.6, and Gd9.33 0.67(SiO4)6O2 = 446.9 ± 21.9. Reference data were used to calculate the standard enthalpies of formation from the elements, ΔH0 f (kJ/mol): La9.33 0.67(SiO4)6O2 = 14611.0 ± 19.4, Nd9.33 0.67(SiO4)6O2 = 14661.5 ± 32.2, Sm9.33 0.67(SiO4)6O2 = -14561.7 ±; 20.8, and Gd9.33 0.67(SiO4)6O2 = -14402.7 ± 28.2. The formation enthalpies become more endothermic as the ionic radius of the lanthanide ion decreases.

Energetics of rare-earth-doped hafnia

2007 ◽  
Vol 22 (4) ◽  
pp. 876-885 ◽  
Author(s):  
Petra Simoncic ◽  
Alexandra Navrotsky
Keyword(s):  
Rare Earth ◽  
Solid Solutions ◽  
Energy Difference ◽  
Solution Calorimetry ◽  
Interaction Parameters ◽  
Enthalpies Of Formation ◽  
Amorphous Phases ◽  
Oxide Melt ◽  
Local Structures ◽  
End Members

The enthalpies of formation of rare-earth (RE)-doped Hf1−xRExO2−x/2 solid solutions (RE = Sm, Gd, Dy, Yb; x = 0.25 to 0.62) with respect to the oxide end members, monoclinic HfO2 and C-type REO1.5, were determined using oxide melt solution calorimetry. The enthalpies of formation fit a function quadratic in composition. The strongly negative interaction parameters in all solid solutions confirm a strong tendency for short-range order. Though strongly negative for all systems, the interaction parameters become less negative with increasing ionic potential (decreasing RE radius). Crystallization energetics were investigated for amorphous coprecipitation products with x = 0.4. The energy difference between the crystalline (fluorite and pyrochlore) and amorphous phases decreases with decreasing dopant radius. This suggests that systems doped with small RE ions have more similar local structures in the fluorite and amorphous phases. These observations may result in a smaller kinetic barrier to recrystallization and account for the greater radiation resistance of materials with smaller RE cations.

Enthalpies of Formation of LaMO3 Perovskites (M = Cr, Fe, Co, and Ni)

2005 ◽  
Vol 20 (1) ◽  
pp. 191-200 ◽  
Author(s):  
Jihong Cheng ◽  
Alexandra Navrotsky ◽  
Xiao-Dong Zhou ◽  
Harlan U. Anderson
Keyword(s):  
High Temperature ◽  
Relative Stability ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide

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 LaMO3 (M = Cr, Fe, Co, and Ni). The enthalpies of formation of LaCrO3 and LaFeO3 from oxides (La2O3 and Cr2O3 or Fe2O3) are –70.06 ± 2.79 kJ/mol and –64.58 ± 2.32 kJ/mol, respectively. The enthalpies of formation of LaCoO3 and LaNiO3 from oxides (La2O3 and CoO or NiO) and O2 are −107.64 ± 1.77 kJ/mol and –57.31 ± 2.55 kJ/mol, respectively. All these data are evaluated and found to be consistent with literature values obtained using other methods. The relative stability among these four perovskites decreases in the order of Cr, Fe, Co, Ni.

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.

scholarly journals Thermodynamics of Molybdenum Trioxide Encapsulated in Zeolite Y

2021 ◽  
Author(s):  
Xianghui Zhang ◽  
Andrew Strzelecki ◽  
Cody Cockreham ◽  
Vitaliy Goncharov ◽  
Houqian Li ◽  
...  
Keyword(s):  
Molybdenum Trioxide ◽  
Zeolite Y ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Metal Species ◽  
Enthalpies Of Formation ◽  
Host Interactions ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide

Zeolites with encapsulated transition metal species are extensively applied in the chemical industry as heterogenous catalysts for favorable kinetic pathways. To elucidate the energetic insights into formation of subnano-sized molybdenum trioxide (MoO) encapsulated/confined in zeolite Y (FAU) from constituent oxides, we performed a systematic experimental thermodynamic study using high temperature oxide melt solution calorimetry as the major tool. Specifically, the formation enthalpy of each MoO/FAU is less endothermic than corresponding zeolite Y, suggesting enhanced thermodynamic stability. As Si/Al ratio increases, the enthalpies of formation of MoO/FAU with identical loading (5 Mo-wt%) tend to be less endothermic, ranging from 61.1 ± 1.8 (Si/Al = 2.9) to 32.8 ± 1.4 kJ/mol TO (Si/Al = 45.6). Coupled with spectroscopic, structural and morphological characterizations, we revealed intricate energetics of MoO – zeolite Y guest – host interactions likely determined by the subtle redox and/or phase evolutions of encapsulated MoO.

scholarly journals Development of high-temperature oxide melt solution calorimetry for p-block element containing materials

2020 ◽  
Vol 35 (16) ◽  
pp. 2239-2246 ◽  
Author(s):  
Mykola Abramchuk ◽  
Kristina Lilova ◽  
Tamilarasan Subramani ◽  
Ray Yoo ◽  
Alexandra Navrotsky
Keyword(s):  
High Temperature ◽  
Solution Calorimetry ◽  
Block Element ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
Image Position

Abstract

Thermochemistry of Hf-Zirconolite, CaHf Ti2O7

1999 ◽  
Vol 556 ◽  
Author(s):  
Robert L. Putnam ◽  
Alexandra Navrotsky ◽  
Brian F. Woodfield ◽  
Jennifer L. Shapiro ◽  
Rebecca Stevens ◽  
...  
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Low Temperature ◽  
Adiabatic Calorimetry ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
Capacity Data

AbstractThe formation enthalpy, - 3752.3 ± 4.7 kJ·mol−1, of Hf-zirconolite, CaHfTi2O7, was obtained using high temperature oxide-melt solution calorimetry. Combined with heat capacity data obtained using low temperature adiabatic calorimetry we report the heat capacity (Cp) and the standard molar formation energetics (ΔH°f. elements, Δ S°T, and ΔG°f. elements)for Hf-zirconolite from T = 298.15 K to T = 1500 K. Comparison of Hf-zirconolite with Zr-zirconolite is made.

scholarly journals Development of high-temperature oxide melt solution calorimetry for p-block element containing materials – CORRIGENDUM

2020 ◽  
pp. 1-1
Author(s):  
Mykola Abramchuk ◽  
Kristina Lilova ◽  
Tamilarasan Subramani ◽  
Ray Yoo ◽  
Alexandra Navrostky
Keyword(s):  
High Temperature ◽  
Solution Calorimetry ◽  
Block Element ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide
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