Materials built from MO6 octahedra linked to XO4 tetrahedra are good candidates for studying the different factors that determine the electrode potential. Among them, olivine-like LiMPO4 (M = transition metal) phosphates are especially interesting. When pressure is applied to LiMPO4 (M = Ni and Fe), a phase transition is induced. However, instead of the well-known olivine ⇔ spinel transformation, a transition to a new phase is observed (β‘). The arrangements of the metal ions (including phosphorus) in the two structures are very similar; thus, the main difference between them is due to the oxygen arrangement in a similar matrix. Raman spectroscopy has confirmed the structural model proposed for the high-pressure phase, in particular the modification in the lithium coordination from 6- to 4-fold upon synthesis under pressure. Among the olivines LiMPO4 (M = Mn, Ni, and Fe), the iron-containing one is only active up to 5.1 V. On the other hand, none of the high-pressure materials is electrochemically active; this can be explained by the change in the electrostatic field at the transition metal position.

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The Sanabria appinitic rocks and host migmatites form an unusual, non-peri-batholithic complex in which all the typical members of the appinite suite are present. It differs from most appinitic complexes in the deeper level of emplacement and the close temporal and spatial association with migmatites. Consequently, many in situ relationships that resulted from the invasion of mafic magma into a crustal anatectic zone are extremely well preserved. The complex shows unequivocal relations between members of the appinitic suite and between these and migmatites derived by anatexis of a gneissic formation (Ollo de Sapo gneiss). These relations point to derivation of monzodiorites and biotite diorites by hydrous basalt fractionation combined with fluid-assisted melting of the crustal rocks surrounding the appinitic intrusions. This hydrous basic magma may be derived from an enriched region of the mantle associated with subduction. Petrogenetic models have been tested using a combination of field relations and geochemical data. Despite the complexity of the processes involved, it is concluded that water played an important role in the petrogenesis of the intermediate and mafic magmas. Reaction between monzodiorite melts and the host migmatites was responsible for the generation of a range of intermediate rocks within the complex. The need for water to facilitate magma generation in both the mantle and the crust suggests that melting is linked with subduction. This interpretation has important implications because appinitic magmatism may be considered as indicative of subduction processes involved not only in the generation of the mafic end-members of the suite, but also in the generation of batholiths with which the appinitic rocks are spatially and temporally associated.

Five lithium aluminosilicate compositions in the LAS system have been synthesized and sintered. The coefficient of thermal expansion of the sintered samples has been studied down to cryogenic conditions. Data presented here at cryogenic conditions will be of important value in the future design of new composite materials with very low thermal expansion. The variation of the thermal expansion properties with composition and sintering temperature is studied and discussed in relation with composition and crystal structure.

Lithium aluminosilicate was fabricated by conventional and non-conventional sintering:microwave and spark plasma sintering, from 1200 to 1300 ºC. A considerable difference in densification, microstructure, coefficient of thermal expansion behavior and hardness and Young's modulus was observed. Microwave technology made possible to obtain fully dense glass-free lithium aluminosilicate bulk material (>99%) with near-zero and controlled coefficient of thermal expansion and relatively high mechanical properties 1 (7.1 GPa of hardness and 110 GPa of Young's modulus) compared to the other two processes. It is believed that the heating mode and effective particle packing by microwave sintering are responsible to improve these properties.

Microwave heating is proposed as non-conventional technique for the sintering of optimal lithium aluminosilicate compositions of E-eucryptite system. The coefficient of thermal expansion and mechanical properties of the sintered samples has been studied under the influence of microwave heating.The ad hoc synthesized E-eucryptite together with the microwave sintering Results of the coefficient of thermal expansion of the E-eucryptite ceramics presented here under cryogenic conditions will be of value, for example, in the future design of new composite materials for space applications.

Lithium aluminosilicate powder precursors of compositions Li 2 O:Al 2 O 3 :SiO 2 as 1:1:2; and 1:1:3.11 were synthesized and sintered by the Spark Plasma Sintering technique. The sintering conditions were adjusted to obtain dense ceramic materials in an attempt to avoid the presence of a glassy phase. XRD and SEM images were employed for composition and microstructure characterization. The coefficient of thermal expansion of the sintered samples was studied down to cryogenic conditions. Rietveld quantification was performed with the use of an external standard. Pure beucryptite of different compositions in dense ceramic bodies was obtained with a negative expansion coefficient. #

Composite materials formed by a LAS matrix reinforced with second phases are promising materials in many applications where better mechanical properties than those corresponding to conventional low thermal expansion coefficient materials are required. In this study we will show the capability of the design of a LAS-alumina submicron composite. The main scope of this work is to test the sinterability of the composites and to design a composition for a very low thermal expansion submicron composite. For this purpose, Taimei alumina (TM-DAR) powders and an ad hoc synthesized ␤-eucryptite phase were used to fabricate the composite. XRD phase compositions and microstructures are discussed together with data from dilatometries in a wide temperature range. The results obtained show the possibility of designing a submicron composite with a very low thermal expansion coefficient and improved mechanical properties that can be used in oxidizing conditions.