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The formation of the stoichiometric Nb3Al phase by a solid state reaction of thin Nb/Al multilayers is basically determined by the intermediate formation of a metastable NbAl solid solution. If the nucleation of Nb2Al is avoided, the homogeneity range of the A15 phase can be extended metastably up to about 28 at.% Al. The temperature dependence of the metastable Al-rich A15 phase boundary can be determined by the respective (free) enthalpy curves of the A15 and the bcc phase calculated from the phase diagram.

There are many aspects of materials surface processing ranging from simple heat treatments to ion implantation or laser surface treatments, e.g. the laser-plasma-coating formation in nitrogen gas, which is called laser nitriding. These methods are often very complicated, involving many basic processes and they have to be optimised for the desired application. Nuclear methods can be successfully applied for this task. First, Ag/Fe multilayers can be prepared by pulsed laser deposition employing an excimer laser. The Ag/Fe system is immiscible and sharp interfaces are expected for that reason. Nevertheless, it will be presented that some intermixing occurs which can be seen by conversion electron Mossbauer spectroscopy with the additional trick of preparing a sensitive 5 7 Fe layer at various distances from the interfaces. Several Ag neighbours to the Fe spy-atom can be resolved, whose abundances vary with the location of the 5 7 Fe marker layer. It is found that the intermixing at the bottom and top interface of the Fe layers is asymmetric.

The high-temperature superconductors Y 1 Ba 2 (Cu 1−x Fe x ) 3 O y and Bi 2 Sr 2 Ca 1 (Cu 1−x Fe x ) 2 O y were investigated by X-ray diffraction and Mossbauer experiments, resistivity measurements and thermo-gravimetrical analysis. In the doped “123”-compound the prefered substitution of Fe on the Cu(I) site does not affect the superconducting transition T c at low Fe content much, but leads to an attraction of additional oxygen and to the formation of a microdomain structure. In the Bi-compound the substitution of Fe in the Cu O 2 planes immediately leads to a reduction of T c and to systematically structural changes. In this structure several different Fe-environments exists as well.

The superconducting, structural and magnetic properties of YiBa 2 ( Cu 100− z − Fe z ) 0.03 O 7−δ (O ⩽ x ⩽ 18) were determined by resistive and magnetic measurements as well as by X-ray diffraction experiments and thermogravimetrical analysis. Four Fe-concentration regimes can be distinguished: Below x = 2 T c remains constant, above 2.3 % Fe contents T c decreases linearly with x, first with 5.4 K jat% Fe and above x 10 with 9.0 Kiat% Fe. Above 15 at% Fe no superconductivity could be detected. This behaviour of T coincides with changes in the structure and the oxygen contents of the Y 1 Ba 2 ( Cu 100− x − Fe x ) 0.03 O 7−δ . Below 2.3 at% the orthorhombic perovskite structure is retained. At larger Fe concentration a tetragonal structure is attained with a = b /3 below x = 10 and with a = b = c /3 above x = 15. Between 10 and 15 at% Fe c /3 approaches the value of a = b . Magnetic measurements show an anomaly below T c , which indicates antiferromagnetic ordering. The magnetic ordering temperature increases with Fe concentration.

Superconducting Y Ba Cu O and Bi Sr Ca Cu O films have been grown in-situ on Si-substrates by KrF excimer laser ablation. Substrate temperatures between 700 and 750 °C and an oxygen partial pressure of about 0.1 mbar are required during deposition in order to obtain completely c-axis oriented Y1Ba2Cu3Oy films on Si, which exhibit superconductivity with an onset at 90 K and zero resistance at 78 K. Under these “optimum” conditions the occurence of the c-axis orientation can be obtained on a variety of substrates, such as Si, SiO2, Al2O3, Zr-foil or even polycrystalline stainless steel. The orientational selection on these substrates originate from a prefered grain growth in c-direction. Furthermore, the same conditions have been applied to the growth of entirely c-axis oriented Bi2Sr2Ca1Cu2O8 and Bi2Sr2Ca2Cu3O10 films on Si.

Fe doped Y 1 Ba 2 Cu 3 O y samples were investigated by in-situ X-ray experiments, Mossbauer spectroscopy and resistivity measurements. Two different orthorhombic-to-tetragonal transitions - induced by annealing experiments at the oxygen content of about 6.5 and by a Fe-substitution of about 2.3 %, respectively - occur. In the first case the decrease of the oxygen content leads to a drastic reduction of T c and in the Mossbauer spectra only one Fe site remains. Contrary to that with increasing Fe-concentration T c only slightly decreases at the orthorhombic-to-tetragonal transition and the occupation of the different Fe sites changes.