Yoichi Hanayama

Measurement of Ultrasound Velocity in the Single Crystal of Black Phosphorus up to 3.3 GPa Gas Pressure

The effect of hydrostatic pressure on the elastic constants of the single crystal black phosphorus is studied by using a gas pressure apparatus. Neon gas is used as the pressure transmitting medium. A large single crystal of orthorhombic black phosphorus with the dimensions of 5×3×6 mm 3 , has been grown under the condition of 1 GPa and 900°C by using a large solid isotropic compression system. The ultrasound wave velocity is measured by a pulse transmission method up to 3.3 GPa. The longitudinal wave velocities along X and Y axes decreased, while that along Z axis increased. An anomaly was observed around 1.7 GPa, which may be attributed to the vanishing of the energy gap of black phosphorus.

Measurement of Ultrasound Velocity in Gases under High Pressures up to 3.5 GPa

Using the high-pressure apparatus described in a previous paper, the freezing points of nitrogen and krypton at room temperature were determined from the volume and ultrasound velocity changes. The ultrasound velocity of neon was also measured up to 3.5 GPa. Taking account of the results of the ultrasound velocity and the volume measurements, empirical formulae for the pressure dependence of ultrasound velocities of helium, neon, argon, krypton and xenon were proposed. The phase diagram of a krypton and helium gas mixture under high pressures up to 1.6 GPa at room temperature was also obtained from the velocity measurement.

Pressure dependence of the elasticity of a steel sphere measured by the cavity resonance method

The pressure derivatives of elastic moduli of a steel sphere were measured by the cavity resonance method, a modified resonant sphere technique under gas pressure using a spherical three-layered structure (3LS) consisting of a sample-thin gas layer–cavity container system. The pressure-induced shifts of resonance peaks of both toroidal and spheroidal modes were observed up to 100 MPa (1 kbar) under gas pressure with helium gas. The resultant pressure derivatives of frequencies of toroidal modes yielded a pressure derivative of shear modulus of ∂G/∂P=2.01±0.08. The pressure derivative of the bulk modulus was determined from the data of spheroidal modes, ∂K/∂P=5.0±0.4, by analyzing these data as free oscillations of the 3LS superimposed on the static compression. The results demonstrate the efficiency of the cavity resonance method for measuring pressure derivatives of elastic moduli of solids.

High Pressure Gas Apparatus for Measuring Ultrasound Velocity in Matters up to 4 GPa

A piston-cylinder apparatus using gases, which could produce hydrostatic pressures of up to 4 GPa and temperatures of up to 800°C is described. A high-pressure tapered cylinder made of 350 maraging steel was 262 mm long and had a 19 mm inside diameter and a working space of 100 mm in length at 4 GPa. The support ring was made of 300 maraging steel and was approximately 180 mm thick and 420 mm in outside diameter. For measurements of both the pressures and temperatures, a manganin gauge and a thermocouple were placed inside the tapered cylinder. No difficulty was encountered with any of these components at pressures of up to 3.5 GPa. This apparatus could be used almost indefinitely, since neither a considerable change of the bore nor surface cracks in the tapered cylinder had been found thus far.

Pressure derivatives of elastic constants of iron by cavity resonance method

Pressure dependence of frequencies of normal modes was measured on a sphere sample of iron(steel) up to 0.1GPa under gas pressure, and pressure derivative of rigidity was obtained, ∂μ/∂P=1.76±0.20. Tentative but reasonable value of pressure derivative of bulk modulus was obtained, ∂K/∂P=5.4±0.5, by assuming the sample‐gas coupling is negligible.