The Use of Transition-Metal Silicides to Reduce the Contact Resistance Between the Electrode and Sintered -Type Mg2Si

The electrical and thermoelectric characteristics of -type Mg2Si equipped with electrodes of Ni and the transition-metal silicides CoSi2, CrSi2, TiSi2, and NiSi were examined. To form the electrodes on the Mg2Si matrix, a monobloc sintering method, i.e., simultaneous sintering of the electrode material during Mg2Si sintering, was used. To obtain dense electrodes and to keep an appropriately low sintering temperature for the Mg2Si matrix, a Ni binder was used for the CoSi2, CrSi2, and TiSi2 monobloc sintering. The mixture ratio between the transition-metal silicide and the Ni was 50:50 in wt.%. The room-temperature - characteristics of the fabricated CoSi2, CrSi2, and TiSi2 electrodes with the Ni binder and NiSi electrodes were considered to be adequate for practical applications in as much as ohmic contacts were obtained. The contact resistance at the Mg2Si/electrode interface decreased by 35% and 28%, respectively, for the CoSi2 and CrSi2 electrodes compared with our standard Ni electrode. The thermoelectric power output was measured at the practical operating temperature of 600 K, with Delta = 500 K. The observed output powers for 3.0 mm x 3.0 mm x 7.5 mm samples equipped with CoSi2, CrSi2, and NiSi electrodes were 153 mW, 149 mW, and 125 mW, respectively, representing increases of 27%, 24%, and 4%, respectively, compared with the 120 mW measured for the sample with Ni electrodes.