White X-ray Nanodiffraction Study of Allotropic Phase Transformation of Hexagonal- into Monoclinic-Cu6Sn5

An allotropic phase transformation of CU 6 Sn 5 from a hexagonal $(\eta)$ to monoclinic $(\eta^{\prime})$ at 186–189 °C is scientifically interesting and technologically important to the microelectronic industry. As $\eta^{\prime}$ lattice is crystallographically pseudosymmetrical with $\eta^{\prime}$ the identifications of $\eta$ and $\eta^{\prime}$ and $\eta$ -to- $\eta^{\prime}$ transformation are extremely difficult via traditional analysis techniques. Herein, we conducted a study to characterize the allotropic phase transformation by Laue diffraction via synchrotron white X-ray nanodiffraction. The results showed that Laue diffraction analysis can well distinguish the two allotropic species $(\eta$ and $\eta^{\prime})$ in spite of the existence of pseudosymmetry in the η-Cu 6 Sn 5 lattice.