Physical chemistry of solids—the science behind materials engineering

Physical chemistry as a bridge between the disciplines: perhaps materials science is that modern field where this function becomes most obvious. Physical chemistry combines fundamental research with advanced technology, and it links the physics of solids and soft matter with the art of chemical synthesis of inorganic, organic or polymer compounds. Its strength is based on the combination of physical methods and concepts with the rich chemical world of molecules and materials—with many specific research fields and methods that can truly be regarded as physicochemical in origin.

It is the challenge and goal of this themed issue to conduct—at the interface between solid state chemistry and solid state physics—fundamental research on the properties of solids and on the scientific methods for their characterization, and to provide in this way the scientific basis for ‘materials engineering’. It is the aim of this themed issue entitled ‘Physical chemistry of solids: the science behind materials engineering’ to report on recent developments in this timely field and to supply high level articles which hopefully are of interest to the general readership of PCCP. It is also driven by this year’s meeting (the Bunsen-Tagung) of the German Bunsen-Gesellschaft für Physikalische Chemie which has the same title.

The 33 papers cover a wide range of problems and materials. Inorganic solids, and in particular complex oxides, play an ever increasing role as advanced functional materials in technological applications nowadays. The defect chemistry of these often nonstoichiometric materials and solid solutions is one of the conceptual backbones, and a number of papers address defect chemical topics. Maier analyzes the ionic and electronic charge transport in nanosized ionic materials in his perspective paper on nanoionics. The study of defects in nanosized systems has become a hot topic, since the size of ionic devices shrinks from the macroscale to the microscale. This technological development is covered in a second perspective paper by Tuller on next-generation power sources. Fitting well to this general subject, Schichtel et al. study the influence of elastic strain on solid electrolyte films with thicknesses on the nanoscale. And they provide a critical view to recent results on extremely high ionic conductivities in ultra-thin films of ionic materials. Heterogeneous catalysis is a field where size effects also play a crucial role: in their paper Sturm et al. report on methanol oxidation on V₂O₅(001)/Au(111) thin films. The paper by Chen et al. on the experimental determination of grain boundary and surface enthalpies of yttria-stabilized zirconia fits well with the general scope of these papers.

Among papers in specific material systems is one hot paper by Myoshi and Martin reporting on B-site diffusivity in a perovskite-type oxide. The cation diffusivity in many oxides is of particular relevance for technical applications at high temperatures, as it governs all processes leading to degradation and long-time failure. Proper understanding of the fundamental atomic transport phenomena is the basis for a successful materials design in solid oxide fuel cells (SOFC), membranes and other high temperature devices. Often electronic properties are as important, and papers by e.g. Nakamura et al., Harvey et al., and Yoo et al. focus on the relation between defect structure and electronic properties. A material which has recently attracted much interest due to its unique combination of properties, namely the calcium aluminate Ca₁₂Al₁₄O₃₃ with a cage structure, is investigated by Lee et al. They present the first comprehensive model for the point defect structure of this material and report systematic data for the ionic and electronic partial conductivities.

Chemical reactions of ionic materials require high temperatures, and the study of these reactions relies on suitable in situ methods. Brendt et al. and Sugak et al. demonstrate state of the art studies with in situ XAS (X-ray absorption spectroscopy) and in situ optical spectroscopy. Electrochemical reactions at much lower temperatures form the basis of modern lithium batteries and polymer fuel cells, and the papers by Indris et al. and Bramnik et al. report results on Li intercalation in some new materials. De Araujo et al. contribute a deep insight into a new polymer material with superior transport properties. The recent success in the understanding of ion dynamics and the resulting spectra is exemplified by Laughman et al. for the case of borate glasses.

A clear and important trend in physical chemistry of solids is the growing number of theoretical studies. Whereas still the majority of these studies are reported by groups from theoretical chemistry, experimentalists start to support their work by computer simulations as the access to powerful software is merely a question of budget. Among nine papers on theory, Woodley et al. and Watkins et al. report on the simulation of complex microporous structures, Agoston and Albe report on point defect energies in indium tin oxide (ITO). Driven by the enormous interest in electrochemical technologies, the simulation of electrode reactions and related processes becomes more and more important. An example from electrocatalysis can be found in the paper by Venkatachalam and Jacob.

Physical chemistry always combines two main strategies: the creation of models and the development of methods. Thus, the impressive and wide range of the topics being covered is an indicator for the success of the underlying physicochemical strategies rather than a symptom of a too diffuse definition of the field.

Finally, we would like to thank all authors for their contribution to this themed issue. We also thank the editorial and production offices for its competent support.

J. Janek, Giessen, Germany

M. Martin, Aachen, Germany

K. D. Becker, Braunschweig, Germany

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