The enthalpy of formation of hafnium dioxide

Kornilov, A. N.; Ushakova, I.M.; Huber, Elmer J.; Holley, Charles E.

doi:10.1016/0021-9614(75)90076-2

Cited by 32 publications

(14 citation statements)

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“…Thus, in the case of HfO 2 previously unaccounted effect of surface energy can make formation enthalpy of bulk material ~20 kJ/mol more exothermic. Ironically, applying that correction to the latest value (−1117 kJ/mol) would bring it close to the very first measurements (−1136 kJ/mol) performed by Roth et al . in 1932.…”

Section: Calorimetrysupporting

confidence: 69%

“…Table compiles data on formation enthalpy of hafnium oxide by different investigators together with reference to thermodynamic tables which adopted particular values. The latest value (−1117.6 ± 6 kJ/mol) is the result of joint effort of Los Alamos Laboratory and Moscow University to resolve the discrepancy between previously published measurements. The initial metal was analyzed for impurities by two different methods and the combustion product was identified as monoclinic HfO 2 .…”

Section: Calorimetrymentioning

confidence: 94%

“…However, monoclinic HfO 2 formed on combustion had surface area large enough that adsorption of H 2 O and CO 2 from air interfered with the measurements. Thus, separate measurements were undertaken to measure H 2 O and CO 2 adsorbed on combustion products upon their exposure to moist air …”

Section: Calorimetrymentioning

confidence: 99%

“…Thus, separate measurements were undertaken to measure H 2 O and CO 2 adsorbed on combustion products upon their exposure to moist air. 110 Note, that after all corrections described above, standard formation enthalpy of hafnium oxide measured in the combustion experiments corresponds to formation for HfO 2 with a non-negligible surface area (SA). Assuming SA = 25 m 2 /g, for monoclinic HfO 2 formed in reaction (1) (which is typical for as-prepared combustion products) and c = 3.7 J/m 2 as measured by solution calorimetry, 111 DH 2 = 19.5 kJ/mol.…”

Section: Calorimetrymentioning

confidence: 99%

“…Enthalpy of formation of refractory multicomponent oxide compounds from constituent oxides cannot be measured directly due to high temperatures and long reaction times needed to form them. However, it can be obtained by measuring heats of solution of compound of interest and constituent oxides, e.g., for La 2 Zr 2 O 7 pyrochlore: 184 Barin 185 À1144.7 ± 1.3 Huber 186 Robie et al 187 À1117.5 ± 2.1 Kornilov 188 Robie and Hemingway 189 À1133.9 ± 6.3 Paputskii 190 À1117.6 ± 1.6 Kornilov et al 110 Refractory oxides, such as ZrO 2 , do not dissolve readily in acid solutions. Solution calorimetry using oxide melts at 700°C-800°C was proved to have precision of traditional aqueous solvent calorimetry, 114 but to be applicable for refractory compounds.…”

Section: (3) Enthalpy Of Formation and Surface Energy Measurements Bymentioning

confidence: 99%

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Experimental Approaches to the Thermodynamics of Ceramics Above 1500°C

Ushakov

Navrotsky

2012

J. Am. Ceram. Soc.

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Traditionally, the nuclear and aerospace industries have been the main drivers behind the development of high‐temperature materials. These applications demand a high degree of reliability and extensive characterization of every new material. There is a lack of experimental thermodynamic data above 1500°C even for HfO2, ZrO2, La2O3, Y2O3, and other constituents of widely used ceramic systems. Such data, as are available, were often obtained half a century ago using custom‐built instruments. We review classic experimental approaches for the measurement of formation enthalpies, high‐temperature enthalpy increments by the drop method, and also discuss more recent developments which include mass spectrometric measurements of vapor pressures, pulsed laser relaxation methods for heat capacity, and melting temperature determination and high‐temperature oxide melt solution calorimetry in application to refractory compounds. Approaches to the experimental determination of phase diagrams at high temperature are introduced using studies of liquid immiscibility in the Zr(O)–UO2 system as an example. Thermal analysis above 2000°C is now possible with commercially available instruments, as shown by the first experimental measurements of the phase transition and fusion enthalpies of La2O3. New results on a premelting phase transition in Y2O3 in oxygen are reported from in situ synchrotron X‐ray diffraction study on levitated samples.

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Section: Calorimetrysupporting

confidence: 69%

Section: Calorimetrymentioning

confidence: 94%

Section: Calorimetrymentioning

confidence: 99%

Section: Calorimetrymentioning

confidence: 99%