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SGTE

Introduction

SGTE is a consortium of European and North-American research organisations working together to develop high-quality thermodynamic databases for a wide variety of inorganic and metallurgical systems. SGTE has been at the forefront of the broader international effort to unify thermodynamic data and assessment methods by promoting use of standard reference data for the elements and binary systems, and generic models to represent the variation in thermodynamic properties with temperature and composition. NPL is a founding member of SGTE.

SGTE data can be obtained via members and their agents for use on personal computers with commercially available software, to enable users to undertake calculations of complex chemical and phase equilibria efficiently and reliably. Members of SGTE have played a principal role in promoting the concept of ‘computational thermochemistry’ as a time- and cost-saving basis for the control and modelling of various types of materials process. In addition, such calculations provide crucial process-related information regarding the nature, amounts and distribution of environmentally hazardous substances produced during the different processing stages.

SGTE Databases

SGTE have developed a number of thermodynamic database for a wide range of technologically important materials. Such databases contain critically assessed data, a set of model parameters which describe as accurately as possible experimental thermodynamic and phase diagram data for binary, ternary systems and higher order systems. The models are based on physical principles which make it possible to extrapolate the critically assessed data to commercially important multi-component systems. Extrapolation from several assessed lower order systems require that these systems are internally consistent and this take time and effort to achieve. At present, a number of commercially interesting as well as scientifically challenging materials have been collected into databases which are available and listed below. The SGTE Databases are under continuous development.

SGTE databases include

·         The SGTE Pure Substance Database containing assessed thermochemical data for about 4000 condensed compounds or gaseous species.

·         The Unary database containing assessed thermochemical data for all stable and many metastable modifications from 298.15 K up to the gaseous state for many elements. These descriptions of the thermodynamic properties of the elements are used as a basis for all SGTE databases.

·         The SGTE Solution database which contains data for the liquid phase and various crystalline phases of the pure elements in addition to over 400 binary, ternary and quaternary alloy systems. The data have been derived by a process of critically assessment taking all the relevant experimental data, eg enthalpies of mixing, partial pressures, solubilities, thermal arrests etc and then using them to derive a small number of coefficients representing how the thermodynamic properties of the system change with temperature and composition.

·         The SGTE Thermal Barrier Coating database was developed in the Max-Planck-Institute Institute for Metal Research in Stuttgart. It covers the system ZrO2-Gd2O3-Y2O3-Al2O3 and is suitable for calculations between 300 K and 3000 K, but in particular above 1100 K. Most of the phases stable in the system are solid solutions described using the compound energy formalism. The liquid phase was described using the two-sublattice partially ionic liquid model. Yyttria stabilised zirconia (YSZ) itself has various industrial applications. For example, the phase with the fluorite structure is used as a solid electrolyte. The tetragonal phase with 6-8 wt. % Y2O3 is used as a thermal barrier coating (TBC) on a metal substrate. Co-doping of the traditional YSZ with Gd enhances the insulating efficiency of thermal barrier system. A thin layer of alpha-Al2O3 (thermally grown oxide, TGO) forms between metallic bond coat and the TBC in the process of thermal cycling. Therefore, phase relations in the ZrO2-Gd2O3-Y2O3-Al2O3 system are important to understand the interactions between TBC and the TGO, stability issues of TBC materials and interactions within multilayer TBC.

·         The SGTE database for molten salt systems was based partly on a compilation of data for Alkali metal halides from Sangster and Pelton but modified considerably to present self-consistent modelling of data across complete compositions ranges.

·         The SLAG database consists of data for the liquid slag and condensed oxides for the Al2O3-CaO-FeO-Fe2O3-MgO-SiO2 system. Recently, data for Na, Cr, Ni, P and have been added and thus allow calculation of sulphide capacities of slags. The liquid slag is described with the cell model proposed by Kapoor-Frohberg and modified by Gaye. Composition variations in the solid oxides have not been taken into account.

·         The III-V semiconductor database contains the 15 possible binary systems between the group III elements Al, Ga and In and the group V elements P, As and Sb.

·         The noble metal alloy database contains evaluated thermodynamic parameters for alloys of Ag, Au, Ir, Os, Pd, Pt, Rh, Ru alloyed amongst themselves and also in alloys with the metals Al, As, Bi, C, Co, Cr, Cu, Fe, Ge, In, Mg, Ni, Pb, Sb, Si, Sn, Ta, Te, Ti, Tl, Zn, Zr. The database provides a good starting basis for development of data for higher-order noble metal systems. At the same time, the assessed data it contains for the binary and ternary sub-systems of Au-Pd-Pt-Sn allow calculations relevant to dental alloy development.

·         The SGTE Nuclear Database has been generated as part of a much bigger database effort to cover many thermochemical aspects related to the field of nuclear reactors. This database is specially made for the investigation of in-vessel chemical reactions. The elements included in the database are O, U, Zr, Fe, Cr, Ni, Ar, H. Also included are systems formed among the 6 oxides UO2, ZrO2, FeO, Fe2O3, Cr2O3, NiO. The database covers the entire composition range from pure metal to oxide regions and contains critically evaluated thermodynamic parameters for all relevant multicomponent condensed or gaseous substances and solution phases.

SGTE Logo

SGTE Publications

SGTE has also been involved in publication of data through the Landolt Börnstein series. Two sets of volumes have been produced so far dealing with:

·         Subvolumes A Pure Substances

·         Subvolumes B Binary systems

A future set of subvolumes is under way covering specific ternary systems relevant to technologically important classes of materials.

Pure Substances - Subvolume A: Heat Capacities, Enthalpies, Entropies and Gibbs Energies, Phase Transition Data

·         A. Elements and Compounds from AgBr to Ba3N2

·         B. Compounds from BeBr‹g> to ZrCl2‹g>

·         C. Compounds from CoCl3 to Ge3N4

·         D. Compounds from HgH‹g> to ZnTe‹g>

Binary Systems - Subvolume B: Phase Diagrams, Phase Transition Data, Integral and Partial Quantities of Alloys

·            A. Elements and Binary Systems from Ag-Al to Au-Tl

·            B. Binary Systems from B-C to Cr-Zr

·            C. Binary Systems from Cs-K to Mg-Zr

·            D. Binary Systems from Mn-Mo to Y-Zr

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The new version of the SGTE Casebook has now been published including a number of contributions from NPL. The first edition of the book was published in 1996 and showed how thermodynamic calculations can be used as a basic tool in the development and optimisation of materials and processes of many different types. Since then the field of 'computational chemistry' has exploded as the reliability and scope of commercial databases have grown, as software packages have been developed to cover kinetic considerations and as more scientists have been acquainted with the potential that the field offers for understanding and modelling industrial and environmental processes. The examples covered in this much expanded book are, to a large extent, real case studies dealt with by members of SGTE and their collaborators in the course of their work.

 

Updated 25 February 2010