Program/Scientific Program
Microsymposia

Materials and Minerals - All theoretical and practical aspects of phase transitions induced by external stimuli (temperature, pressure, electric and magnetic fields…) and their potential applications.

materials from high quality powder diffraction data, and on the assistance of other methods, both experimental and theoretical.

practical reality and may be the only information available. Using such data has its own set of challenges to maintain chemical and structural reasonableness in what may be the only known structure for a particular compound.

atomic order/disorder at the long- and short-range level, real structures with defects and modulation, structural modularity (polytypism, polysomatism), growth twins, low crystallinity and disordered materials.

methods aimed at increasing the useful content that can be extracted by Rietveld refinement. The development of parametric methods gives the possibility of constraining refinements to chemically or physically plausible solutions, and of directly refining non-crystallographic parameters. The addition of symmetry constraints further reduces the number of refined variables to increase the feasibility and precision of increasingly complex problems using powder diffraction data.

nanopolycrystalline diamond and other superhard materials, hydrogen storage materials, noble gas compounds and other exotic compounds from high pressure synthesis, high pressure nitride synthesis, carbon dioxide sequestration at high pressure, superconductors, exotic forms of elements, high energy density materials.

properties and crystal growth process. To control crystal growth process, and ultimately - crystal quality, it is important to understand numerous related to crystal symmetry phenomena which are observed during crystal growth - for both, inorganic and organic compounds.

Crystal habit and kinetic effects like growth rate anisotropy can influence quality of bulk crystal grown from liquid and shape of growing crystal very often has to be controlled for practical applications. These difficulties are know to be enhance in the case of layered crystals, partially due to limits of the mass transport for different facets present on solid-liquid interface. Quite often phase transitions are observed during cooling crystals grown at elevated temperatures. Nucleation of a new phase can lead to various forms of twinning, creation of domains in ferroelectric, piezoelectric and magnetic materials, including exotic morphotropic phases (like in relaxor type ferroelctrics) are examples of symmetry related phenomena which can significantly influence quality of crystal.

Isomorphism is also one of the key concepts of crystallography and structural chemistry. Isomorphic substitution is a very powerful and flexible tool to control the properties of materials, stabilize their desired crystal structure and optimize the conditions of their synthesis. This phenomenon exists in various forms, such as isovalent/heterovalent isomorphism as well as cationic/anionic and combined cationic-anionic isomorphism, that are well represented among natural and man-made materials.

strengthen the interactions between the fields of high-pressure crystallography, crystal growth and strongly correlated electron systems. Multiferroics are extremely interesting materials, with numerous possible applications. Their complex transport and structural properties make them a playground for the material science community. In this contest, the role of high pressure synthesis is fundamental both as bulk material, to stabilize metastable or highly distorted structures (mainly complex perovskite) and as single crystals, to correlate the structural properties and the magnetic and electric coupling.

of the field and related synthetic inorganic structures ranging from the synthesis and crystal growth to the characterization of the structures and properties, through modelling and development of new methods.

phenomena in complex oxides and related materials, studied by X-ray and neutron scattering and other techniques.

crystal growth, characterization and devices of widegap semiconductors such as GaN, AlN and SiC. The crystals play an important role for energy and environment in the world in the present time. The minisymposium will contain topics of crystal growth including physical vapor transport (PVT), liquid phase epitaxy (LPE) and chemical vapor deposition (CVD) and etc., and characterization using X-ray by synchrotron radiation and atomic force microscopy. Moreover, characterization of devices using the widebandgap semiconductors in operation condition will be discussed.　

Furthermore, several metal oxides such as ZnO, Beta-Ga2O3, In2O3, SnO2 are semiconductors, but their application for active electronic devices is still scarce. ZnO based varistor ceramics are an example where p-n junctions are created between the n-type ZnO grain and the heavily doped (typically Bi3+) p-type intergrain matrix. Indium-tin oxide (ITO) or Al3+,Ga3+:ZnO have wide applications as transparent conducting electrodes for photovoltaics or flat-panel displays. Interfaces between SrTiO3 and LaAlO3 show extreme high electron mobility exceeding 10,000 cm2/Vs at low temperatures. So far, the following points are established: (1) Transparent conducting oxides (TCO’s) and transparent semiconducting oxides (TSO’s) are with a few exceptions available as polycrystals or thin layers only; (2) transport properties are significantly governed by surface structure and electronic surface states; (3) most TCO’s are intrinsic n-type semiconductors and p-type doping is either impossible, or possible only at surfaces or other defects; (4) the previous point has some exceptions: CuAlO2, SnO, and a few other materials are p-type. It is the aim of the proposed microsymposium to focus the attention of the crystallographic community on this promising group of materials. Special attention should be put on the following issues: structural defects (origin and influence on electronic properties), surfaces and interfaces (electronic surface states, reconstruction), epitaxy (perhaps the only promising way to create p-n junctions in TSO’s), phase transformations (e.g. the ferroelectric transformation of SrTiO3).