Effect of Argon Pressure on the Sublimation Rate of Magnesium

The sublimation rate of magnesium in an argon atmosphere with pressures ranging\u27 from 10- 11 up to 760 mm Hg was measured. At pressures from 10-6 to 10- 2 mm Hg the sublimation rate is approximately constant. It considerably decreases at higher pressures. At pressures of about 102 mm Hg the sublimation rate of magnesium is very low. As the transfer of vapour from the surface of the sample to the condenser takes place by diffusion at higher pressures and by molecular flow at lower pressures, it is not possible to treat the problem uniformly. The results of the present experiments are therefore related to some approximative equations

Effect of Argon Pressure on the Sublimation Rate of Magnesium

The sublimation rate of magnesium in an argon atmosphere with pressures ranging\u27 from 10- 11 up to 760 mm Hg was measured. At pressures from 10-6 to 10- 2 mm Hg the sublimation rate is approximately constant. It considerably decreases at higher pressures. At pressures of about 102 mm Hg the sublimation rate of magnesium is very low. As the transfer of vapour from the surface of the sample to the condenser takes place by diffusion at higher pressures and by molecular flow at lower pressures, it is not possible to treat the problem uniformly. The results of the present experiments are therefore related to some approximative equations

On the Preparation of Some Group I-VI Semiconducting Compounds

A new method for the preparation of cuprous and silver sulphide, selenide and telluride is described. The method provides a stage of purification of the nonmetallic component, which is in most cases a carrier of uncontrolled impurities. The variation of composition by preferential evaporation in vaccum is described and two methods for measurement of stoichiometry are given: measurement by weighing and measurement by electrical conductivity, if the relation composition vs. conductivity is known. Single crystals can be easily obtained only in the case of cuprous sulphide and selenide

Electrical Conductiviti of Semiconducting Na2Te

A n ew method for the preparation of the semiconducting compound Na2Te as well as electrical conductance measurements in the ,system Na-Te 1is described . The composition of the samples nearly corresponded to Na2Te, but with a small excess of tellurium. The conductance of each sample was measured three times. Between consecutive measurements the excess quantity of tellurium was gradually reduced by evaporation of the liquid phase, until the remaining sample had the exact composition Na2Te. All measurements were carried out betwee n room temperature and 62QOC. The experimental curves were fitted mathematically. The most plausible explanation of conductance variation with temperature appears to be the following. The samples exhibit mixed ionic conduction of Na2Te 2 a nd Na2Te6, and intrinsic electronic c01I1duction of Na2Te. Caracterist ic activation energies for ionic conduction were calculated. For Na2Te the energy gap E g = 2.3 eV

On the Preparation of Some Group I-VI Semiconducting Compounds

A new method for the preparation of cuprous and silver sulphide, selenide and telluride is described. The method provides a stage of purification of the nonmetallic component, which is in most cases a carrier of uncontrolled impurities. The variation of composition by preferential evaporation in vaccum is described and two methods for measurement of stoichiometry are given: measurement by weighing and measurement by electrical conductivity, if the relation composition vs. conductivity is known. Single crystals can be easily obtained only in the case of cuprous sulphide and selenide

Electrical Conductiviti of Semiconducting Na2Te

A n ew method for the preparation of the semiconducting compound Na2Te as well as electrical conductance measurements in the ,system Na-Te 1is described . The composition of the samples nearly corresponded to Na2Te, but with a small excess of tellurium. The conductance of each sample was measured three times. Between consecutive measurements the excess quantity of tellurium was gradually reduced by evaporation of the liquid phase, until the remaining sample had the exact composition Na2Te. All measurements were carried out betwee n room temperature and 62QOC. The experimental curves were fitted mathematically. The most plausible explanation of conductance variation with temperature appears to be the following. The samples exhibit mixed ionic conduction of Na2Te 2 a nd Na2Te6, and intrinsic electronic c01I1duction of Na2Te. Caracterist ic activation energies for ionic conduction were calculated. For Na2Te the energy gap E g = 2.3 eV

On the optimization of the large magnetoresistance of

We describe an attempt to find the key parameter for the optimization of recently discovered large magnetoresistance in non-stoichiometric silver chalcogenides. Our measurements of the resistivity, magnetoresistance and the Hall effect of Ag2Se and their simple analysis lead us to the conclusion that the most important optimization variable is the Hall mobility of the charge carriers. We suggest that the largest magnetoresistance may be expected in the samples with the Hall mobility equal to about $0.1\,$m2/Vs