The martensitic transformation temperatures and the types of martensitic phases have been determined in a wide concentration range of technological interest for Cu-Al-Ni shape-memory alloys (SMAs) A stability diagram of martensitic phases as a function of alloy concentration has been determined. It is found that when the aluminum content increases, the transformation changes from ␤ 3 ⇒ ␤ Ј 3 to ␤ 3 ⇒ ␥ Ј 3 , with an intermediate concentration range where both martensites coexist due to a ␤ 3 ⇒ ␥ Ј 3 ϩ ␤ Ј 3 transformation. On the other hand, an increase of nickel content stabilizes the martensite ␤ Ј 3 , changing from a mixed ␤ 3 ⇒ ␥ Ј 3 ϩ ␤ Ј 3 to a single ␤ 3 ⇒ ␤ Ј 3 transformation. Furthermore, linear relationships between M s and Al and Ni concentrations have been obtained for all types of martensitic phases.

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Slow diffusion of aqueous solutions of europium() chloride into gel of sodium metasilicate containing malonic acid (H 2 mal) yields single crystals of the three-dimensional compound of formula [Eu 2 (mal) 3 (H 2 O) 6 ] whose structure was determined by X-ray diffraction methods at 293 and 173 K. It crystallizes in the monoclinic system but the spatial group changes from I2/a in the high temperature range (293 ≥ T ≥ 236 K) to Ia in the low temperature range (T < 236 K). In both cases, nine oxygen atoms forming a distorted monocapped square antiprism surround the Eu 3ϩ ions. The structure at 293 K consists of a three-dimensional arrangement of triaquaeuropium() units bridged by malonate groups which result from cross-linking of the single chains running parallel to the c axis and the double zigzag chains which grow in the ab plane. At low temperature the structure of the compound can be visualised as chains of europium() ions linked through two of the three crystallographically independent malonate ligands, whose chains run parallel to the b axis and a second family of chains (along the c axis) through the third independent malonate ligand forming a three-dimensional network. In both the crystal structure is stabilised through extensive hydrogen bonding involving carboxylate and water molecules. Studies of the magnetic behaviour, spectroscopic, thermogravimetric and calorimetric characteristics of [Eu 2 (mal) 3 (H 2 O) 6 ] are reported. Laser-excited site selective spectroscopy shows a unique crystal-field site for Eu III ions in the crystal at room temperature and down to 236 K. However, below this temperature, two different sites are clearly identified, in agreement with a change in the crystal structure.

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