Although many challenges of the 21st century need solutions which are directly connected with the development of new technologies, the preferences of prospective students in Germany are often far from mathematics, physics and chemistry. Moreover, the acceptance and recognition of new achievements in these disciplines are quite low in society, even if these achievements are the basis for the development of new technologies that positively affect daily life. As a part of a campaign intended to increase the number of students in the fields of materials science and materials technology (and related fields), the authors created an escape room focused on materials science and crystallography, which illustrates the approaches used by materials scientists and the beauty of crystallography. The fundamental features of the escape room, which are presented in this contribution, are its variability and the ability to inspire participants who have different backgrounds in physics, chemistry and/or materials science. By varying the level of difficulty and the game play duration, the escape room structure makes it possible to appeal to a broad audience, offer an authentic escape room experience and impart lasting knowledge through reflection after completion. The authors' experiences with the escape room and the feedback from the attendees are summarized at the end of the contribution.

Currently available Cu-Nb-Sn phase diagrams lack the recently discovered nausite phase (Cu,Nb)Sn2, which is an important intermediate in the course of thermal processing of superconducting Nb3Sn wires. Processing decisively determines the resulting microstructure of Nb3Sn and, thus, its superconducting properties. Lack of suitable and complete phase diagrams, however, obstructs rational design of such thermal processing procedures. To close this gap and to obtain valid knowledge of homogeneity and stability range of nausite, various Cu-Nb-Sn samples, which are heat-treated between 300 degrees C and 500 degrees C, are investigated. By means of energy-dispersive Xray spectroscopy (EDX), a temperature-dependent homogeneity range of nausite is observed, which covers average mole fractions of Cu between 0.09 and 0.15. This is correlated with a change in the mean atomic volume and can be seen in the lattice parameters determined by X-ray diffraction (XRD). Additionally performed firstprinciples calculations on different CuSn2 and NbSn2 model structures confirm this trend. Furthermore, the peritectic decomposition of nausite to NbSn2 and liquid at 586 degrees C is determined by means of in situ XRD and differential scanning calorimetry (DSC). By using the CALPHAD (CALculation of PHase Diagrams) approach, all these findings are used to extend a previous thermodynamic description of the Cu-Nb-Sn system by including the nausite as an additional phase. With this noteworthy integration, the updated modelling of the Cu-Nb-Sn system can be used for optimizing the multistage heat-treatment steps during processing superconducting Nb3Sn wires.

In recent years, the phase formation sequence during heat treatment of Nb3Sn wires, and the influence of the microstructure and compositional homogeneity of Nb3Sn on in-field critical current (I-c), have received increasing attention. For RRP wires, the importance of understanding and managing the formation of the ternary phase nausite has been demonstrated. However, a published Cu-Nb-Sn phase diagram including this phase is still not available; and conductor development for the Future Circular Collider (FCC) study has introduced a variety of less-studied internal tin wire layouts. In this article, a study of phase transformations in the ternary Cu-Nb-Sn system is summarized, and selected isothermal sections of the re-evaluated phase diagram are presented. The phase transformations during low-temperature heat treatment steps of wires developed for the FCC study are also presented and analyzed in comparison to established RRP conductors.

Processing of superconducting Nb3Sn multifilamentary wires requires several heat-treatment steps forming Nb3Sn at the final stage. During these heat treatments various intermetallic phases from the Cu–Nb–Sn system were intermediately formed, including a ternary phase, sometimes called “Nausite”. This phase derives from the binary NbSn2 phase by partial substitution of Nb by Cu (Martin et al., Intermetallics 80 (2017) [16], [17], [18], [19], [20], [21]). In this work, several samples containing NbSn2 and Nausite were investigated which show similar growth morphologies for both phases, also with some peculiarities, which are reflected by similarities of their atomic structures. Indeed, both phases belong to closely related crystal structures (CuMg2- and NiMg2-type) with comparable lattice parameters. This leads to similar EBSD Kikuchi patterns which causes difficulties in reliable phase distinction. In order to be able to use EBSD as a useful tool for local phase determination in the sub-μm range, phase distinction will be successful only when distinct minor, less prominent Kikuchi bands can be resolved and were used for indexing. This was revealed in this work using simulated Kikuchi patterns of both phases. Additionally, these bands overcome problems in orientation analysis of NbSn2 which arise from a pseudo-hexagonal symmetry.

The study of next-generation high-energy accelerators based on 16 T dipoles has emphasized the need for higher performance, cost-effective Nb3Sn superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density $(J_{c})$ of 1500 A/mm2 at 16 T and 4.2 K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this paper, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first-stage $J_{c}$ milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize $J_{c}$.