MATERIALS CHARACTERISATION AND DATABASES. Jo Daams, Philips Research, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands

In an industrial research environment where precise and fast characterisation of materials is essential, databases are widely used. Especially in our Materials Analysis Department these databases, providing chemical and physical data, are used on a daily basis. The structure analysis group, consisting of X-Ray Diffraction (XRD) and Electron Microscopy (TEM and SEM), uses databases like the Powder Diffraction Files from the ICDD and there is access to crystallographic databases like CRYSTMET.

In studies involving "new materials", however, these databases are more or less incomplete and to a certain extent not up-to-date. Especially those databases which contain, from an user point of view, perfect data, have the tendency to run some years behind the literature. Therefore, they are as such not very useful in our particular type of research environment. So it is common practise in our work to make our own or to update the existing databases. This part of our work searching for and collecting crystal structural information is rather time consuming due to the fact that for crystallographic data more then a hundred scientific journals have to be scanned. In the presentation some aspects of using databases in materials science will be presented. For example, in some ternary systems about 60 compounds are published (including the elements, binary and ternary compounds). For about 45 of these compounds the crystal structure data has also been published. In the powder diffraction files, however, only 30 powder patterns found in this system are included. Meaning that users, working in this system, have to calculate the other powder patterns in order to make their database complete. In conclusion databases are essential tools in material science especially in a characterisation group. The applicability of the existing databases is, however, strongly hindered by a number of obstacles. It is therefore necessary that the IUCr (representing the users of databases) starts a cooperation with database "manufacturers" in order to obtain up-to-date, correct and easy accessible databases.