Abstract: Provided is a multi-element polycrystal formed by cooling a melt containing multiple components while controlling a cooling rate. The multi-element polycrystal is a mixed crystal essentially formed of elements Si and Ge having different absorption wavelength ranges and having a composition represented by Si1-XGeX, in which Ge absorbs light over a longer range of wavelength from a shorter to longer wavelength range than Si, each of the crystal grains of the mixed crystal has a matrix having a plurality of discrete regions dispersed therein, the average matrix composition is represented by Si1-x1Gex1 and the average composition of the discrete regions is represented by Si1-x2Gex2 where X1<X<X2. Also, provided is a solar-cell polycrystal satisfying high light-absorption efficiency and low cost by using the multi-element polycrystal, a solar cell and a method of manufacturing the solar cell.

Abstract: Provided is a multi-element polycrystal formed by cooling a melt containing multiple components while controlling a cooling rate. The multi-element polycrystal is a mixed crystal essentially formed of elements Si and Ge having different absorption wavelength ranges and having a composition represented by Si1-XGeX, in which Ge absorbs light over a longer range of wavelength from a shorter to longer wavelength range than Si, each of the crystal grains of the mixed crystal has a matrix having a plurality of discrete regions dispersed therein, the average matrix composition is represented by Si1-x1Gex1 and the average composition of the discrete regions is represented by Si1-x2Gex2 where X1<X<X2. Also, provided is a solar-cell polycrystal satisfying high light-absorption efficiency and low cost by using the multi-element polycrystal, a solar cell and a method of manufacturing the solar cell.

Abstract: A rock drill having a hydraulic system for controlling a striking, rotating and advancing movements of a drilling rod. The advancing or forward feeding conduit for a feed actuator is provided with a relief valve which is responsive to the pressure in the positive rotating conduit for a rotary actuator so that the pressure in the forward feeding conduit is relieved to weaken the advancing force when the load on the rotary actuator is increased. A further relief valve is also provided for relieving the pressure in the striker conduit to weaken the striking force. A switching valve is provided between the advancing and retreating conduits for the feed actuator so that the direction of movement of the feed actuator is automatically changed when there is an abrupt decrease in the pressure in the striker conduit.