New apparatus for precise electrical transport measurements under quasi-hydrostatic pressures up to 15 GPa

We report a technique for the precise measurement of electrical resistivity under high pressures up to 15 GPa by using Bridgman anvils. The relatively large size of the pressure chamber (1.0 mm in diameter) allows the use of large specimens and simple experimental procedures rather than using a standard diamond anvil cell. A SUS310 gasket is pressed by two tungsten carbide anvils. A sample with typical dimensions of approximately 0.5x0.2x0.1 mm(3) is placed in a small hole of the gasket. In order to obtain a quasi-hydrostatic pressure, the pressure chamber is filled with a 1: 1 mixture of Fluorinert FC70 and FC77 as the pressure transmitting medium. Electrical leads are introduced through shallow grooves milled into the anvil. The grooves are filled with a mixture of alumina powder for insulation. Accurate data of the resistance values of Bi and Fe at room temperature are available. We observe sharp transitions for Bi at 2.55, 2.7, and 7.7 GPa. The electrical resistance of Fe shows a sudden increase due to a structural transition near 14 GPa.