Indium solubility in α-gallium and gallium-indium eutectic alloys studied using PAC
The melting temperature in α-gallium is 303K. The method of perturbed angular correlation of gamma rays (PAC) was used to determine the solubility of 111In probe atoms present at of 10-10 mole fraction. Below 303K and above the eutectic temperature of the gallium-indium binary system, approximately 10% of probes were observed through measurements of nuclear quadrupole interactions to be dissolved in solid gallium. This makes the terminal solubility about 10-11. Below the eutectic temperature, where the only stable phases are gallium and indium metals, the remaining 90% of indium probes, previous being in the liquid phase, were observed to crystallize into tetragonal indium metal, forming crystals of radioactive 111In. In other experiments, about 1% of natural indium or other elements were added to the sample to see their effects on the eutectic reaction. It turns out that bismuth, cadmium and zinc precipitate independently of indium, while tin precipitates with indium. Cadmium-indium alloy at indium-rich region was also studied. Transformation between αT and αK phases are observed. The effect of cadmium impurities on indium metal signal is observed to be small. Mercury-indium system at mercury-rich region was also studied as another example of studying the boundary of binary phase diagram using PAC technique. The terminal solubility of indium in solid mercury was found to be greater than the 10-8 mole fraction of 111In in the samples.