Preparative strategies

Availability of pure, well-characterized solid samples is crucial to all solid state studies. A knowledge of the various experimental methods available for the preparation of solids therefore becomes an important and integral part of solid state chemistry (Corbett, 1987; Hagenmuller, 1972; Honig & Rao, 1981; Rao, 1994). A brief reflection on the development of solid state science reveals that, in many cases, it is the synthesis of a novel compound that has triggered off a new line of research. Tables 3.1 and 3.2 provide a few examples to illustrate the point. To many solid state scientists, preparation of solids may mean preparation of single crystals of elements or simple compounds (e.g. Si, Ge, III-V semiconductors, alkali halides, etc.) for a study of a specific property or for technical applications. Preparation of solids is, however, a much more general activity, particularly amenable to chemists. A variety of strategies are adopted to prepare solids and to grow crystals. Technological advances have enabled solid state chemists to employ a broad range of conditions for preparative purposes. Ultra-rapid quenching of materials from very high temperatures, irradiation heating by intense laser beams, melting of solids by electron-beam heating or by the skull method and use of high pressures have become common procedures. Thus, by employing high-power CO2 lasers (> 1200 W) several entropy-stabilized metastable (e.g. α-CaCr2O4, BaNi2In8O15) and mixed-valent oxides (e.g. Sr7Nb2IVNb4VO21 and Ba2TiIII12TiIVO22) have been synthesized (Möhr & Müller-Büschbaum, 1995).