**Section 5**

**General Issues in Crystallization** 

490 Advances in Crystallization Processes

Usdowsky E. 1973 – Das geochemische Verhalten des Strontiums bei der Genese und

Veizer J. 1989 – Strontium isotopes in seawater through time. Ann. Rev. Earth Plan. Sci., 17:

White J.C. & Mawer C.K. 1988 – Dynamic recrystallisation and associated exsolution in perthites: evidence of deep crystal thrusting. J. Geophys. Res., 93: 325-337. Wilson A.H. & Versfeld J.A. 1994 – The Elary Archaean Nondweni greenstone belt, southern

Warren 1999 – *Evaporites – their Evolution and Economy*. Blackwell Science, 438 pp. Warren 2006 – *Evaporites: Sediments, Resources and Hydrocarbons*. Springer, 1035 pp.

and depositional environment: Precambrian Research, 67: 243-276.

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Kaapvaal Craton, South Africa; Part I, Stratigraphy, sedimentology, mineralization

**19** 

*1Spain 2Perú* 

**Synthetic Methods for Perovskite Materials** 

Solid state chemistry thrives on a rich variety of solids that can be synthesized using a wide range of techniques. It is well known that the preparative route plays a critical role on the physical and chemical properties of the reaction products, controlling the structure, morphology, grain size and surface area of the obtained materials (Cheetham & Day, 1987; Rao & Gopalakrishnan, 1997). This is particularly important in the area of ABO3 perovskite compounds given that they have for long been at the heart of important applications. From the first uses of perovskites as a white pigments, PbTiO3 in the 1930's (Robertson, 1936) to the MLC capacitors (mostly based in substituted PbTi1-xZrxO3 or BaTiO3 materials) in which today's computers rely on to operate, synthetic methods have been a key factor in the

Traditionally, most of these ceramic materials have been prepared from the mixture of their constituent oxides in the so called solid state reaction, "shake and bake" or ceramic method, a preparative route for which high temperature is a must in order to accelerate the slow solid–solid diffusion (Fukuoka et al., 1997; Inaguma et al., 1993; Safari et al., 1996). Despite its extended use in practically all fields in which perovskite-structured materials are needed, not all applications are better off with this method since the low kinetics and high temperature also yield samples with low homogeneity, with the presence of secondary phases and with uncontrolled (and typically large) particle size of low surface area which are undesired for some applications such as in gas sensors or in catalysis where small particles and high surface area are needed (Bell et al., 2000). This conventional route, however, is widely employed due to its simplicity and low manufacturing cost. Nevertheless, with appropriate optimisation, as when softmechanochemical processing is used prior to calcinations at high temperature (Senna, 2005), the method results in high quality single phase perovskites that can be used in

optimization of their final properties (Pithan et al., 2005).

**1. Introduction** 

electroceramic applications.

**– Structure and Morphology** 

Ana Ecija, Karmele Vidal, Aitor Larrañaga,

*Sección Químicas, Lima,* 

Luis Ortega-San-Martín and María Isabel Arriortua

*1Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Facultad de Ciencia y Tecnología, Dpto. Mineralogía y Petrología, Leioa, 2Pontificia Universidad Católica del Perú (PUCP), Dpto. Ciencias,* 
