| Popis: |
It is necessary to know the values of the thermal conductivity coeffi cient of a semiconductor material to assess the possibility of its application as a thermoelectric. The thermal conductivity of natural minerals of galena (PbS), chalcopyrite (CuFeS2), and ZnS ceramics was studied using the absolute stationary method of longitudinal heat fl ux in the range of 50–300 K. The samples were homogeneous, had low impurity content (the chemical composition of the samples was controlled by the X-ray fl uorescence method) and were characterized by high electrical resistivity (r > 9·10–2 Ohm·m at room temperature). It corresponds to the electronic component of the thermal conductivity ke < 1·10–4 W/(m·K). The results of the thermal conductivity measurements are presented graphically and in tabular form. All the dependences are shown to be decreasing. The thermal conductivity values (W/(m·K)) at 50 K amount to 10.9 for PbS, 62 for CuFeS2, and 73-98 for ZnS. At 300 K the values are 2.48, 10.5 and 18.6 – 18.8 W/(m·K), respectively. All the studied materials have much worse thermal conductivity than pyrite (FeS2). The obtained data was compared to the data available in literary sources. The temperature dependence of the thermal сonductivity of galena is low, its low thermal conductivity is favourable for thermoelectric applications. The thermal conductivity of chalcopyrite, which was detected in this study, appeared to be the highest among the corresponding literature data. The high thermal conductivity of zinc sulphide correlates to its wide variability depending on the structural features of the material. The temperature dependences of the mean free path of phonons were calculated. The values of this characteristic, estimated for the melting temperature, for PbS and for ZnS, in particular, signifi cantly exceed the size of an elementary crystal cell, which is unusual. |
