Transmission electron microscopy study of a dental gallium alloy

Analytical transmission electron microscopy (TEM) studies of a dental gallium alloy have been carried out. This commercial Ga alloy was made by triturating a Ag-Sn-Cu-rich alloy powder with a liquid Ga alloy containing Ga, In and Sn. Ga alloys are of increasing interest as an alternative to amalgam. The dental material studied in the present work was found to be a composite consisting of remaining, undissolved particles from the Ag-based alloy powder in a matrix of reaction products with the liquid Ga alloy. The phases in the matrix and the remaining Ag-based alloy particles have been identified by electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectroscopy. the following phases were identified: orthorhombic Ag₃Sn, cubic -Cu₉Ga₄, cubic Ag₉In₄, tetragonal -Sn and hexagonal Ag₂Ga. In addition to these well-known phases Ga-rich regions of Cu-Ga were observed consisting of an intergrowth of the tetragonal CuGa₂ and one of the cubic -Cu₉Ga₄ phases.