Thermochemical insights into refractory ceramic materials based on oxides with large tetravalent cations

Navrotsky, Alexandra

doi:10.1039/b417143h

Cited by 143 publications

(99 citation statements)

References 33 publications

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“…It should be mentioned that [36] obtained enthalpy of formation of pyrochlore by combustion calorimetry ∼10 kJ less negative than was obtained by [16] using solution calorimetry. Navrotsky [37] presented value for enthalpy of formation of pyrochlore from elements ∼−100 kJ mol −1 , which is even less negative than data of [36]. However, the source of data presented in Fig.…”

Section: Binary Systemsmentioning

confidence: 46%

Assessment of thermodynamic functions in the ZrO2–La2O3–Al2O3 system

Fabrichnaya

Lakiza

et al. 2008

Journal of Alloys and Compounds

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Section: Binary Systemsmentioning

confidence: 46%

Assessment of thermodynamic functions in the ZrO2–La2O3–Al2O3 system

Fabrichnaya

Lakiza

et al. 2008

Journal of Alloys and Compounds

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“…The enthalpy and entropy of Nd 2 Zr 2 O 7 were adjusted to make pyrochlore phase more stable thus reproduce data [9] for sample #7 (ZrO 2 -48.46 mol%Nd 2 O 3 -5.38 mol%Y 2 O 3 ), where pyrochlore was found stable at 1673 K. The resulting value for entropy of Nd 2 Zr 2 O 7 became more close to experimental data of Lutique et al [8] and enthalpy of formation more close to experimental data obtained by solution calorimetry in work of Navrotsky. [16] Additionally, DTA investigations for eutectoid composition ZrO 2 -53.85 mol% Nd 2 O 3 and for ZrO 2 -66.67 mol% Nd 2 O 3 composition were performed up to 1973 K in present work. The determined temperature of F = Pyr + A eutectoid reaction (1834 K) is $120 K higher then obtained by hightemperature XRD in study of Rouanet.…”

Section: Optimizationmentioning

confidence: 99%

Phase Relations in the ZrO2-Nd2O3-Y2O3 System: Experimental Study and Advanced Thermodynamic Modeling

Fabrichnaya

Savinykh

Schreiber

et al. 2011

J. Phase Equilib. Diffus.

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Phase equilibria in the ZrO 2 -Nd 2 O 3 -Y 2 O 3 system at 1523-1873 K have been investigated by x-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive x-ray spectroscopy (SEM/EDX). Temperatures of phase transformations were determined by differential thermal analysis. Temperatures of invariant reactions in the ZrO 2 -Nd 2 O 3 system F = A + Pyr and H = F + A were determined as 1763 and 2118 K respectively and thermodynamic parameters of phases were re-assessed. Phase transformations in ternary systems were determined at 1732 K for composition ZrO 2 -48.46Nd 2 O 3 -5.38Y 2 O 3 (mol%) and at 1744 and 1881 K for composition ZrO 2 -79.09Nd 2 O 3 -2.75Y 2 O 3 (mol%). They were interpreted using XRD investigation before and after DTA as Pyr + B fi F, Pyr fi F and A fi B, respectively. The solubility of the Y 2 O 3 in pyrochlore phase was found to exceed 10 mol%. The thermodynamic parameters of the ZrO 2 -Nd 2 O 3 -Y 2 O 3 system were reassessed taking into account solubility of Y 2 O 3 in the Nd 2 Zr 2 O 7 pyrochlore phase (Pyr). It is assumed that Y 3+ substitutes Nd 3+ and Zr 4+ in their preferentially occupied sublattices. Ternary parameter was introduced into fluorite phase (F) for better reproducing of phase equilibria. Mixing parameters were reassessed for phase A (Nd 2 O 3 based solution), monoclinic phase B and cubic phase C (Y 2 O 3 based solution). The isothermal sections calculated for the ZrO 2 -Nd 2 O 3 -Y 2 O 3 system are in the reasonable agreement with experimental results.

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“…The development of the extended (probably twin) defects along planes perpendicular to the growth direction of the nanorods may be related to the tendency of HfO 2 nanocrystals to transform between monoclinic and tetragonal crystal phases. [21] The formation of these defect planes in the nanorods could reflect a high vacancy concentration spread throughout the nanorods or alternatively, may reflect a locally high defect concentration in these planes. Furthermore, the high magnetic anisotropy found by Coey et al in the thin films and the high magnetic anisotropy of the HfO 2 nanorods reflected through their relatively large coercivity can be explained by an anisotropic distribution of defects with respect to the nanorod structure.…”

mentioning

confidence: 99%