SU456199A1 - The method of determining the sign of the small absolute thermo-emf. - Google Patents

Description

one

The invention relates to methods for studying the thermoelectric properties of various materials, mainly metals and alloys.

Usually the sign of absolute thermo-emf. determined by comparing the measured difference in absolute thermo-emf. the studied and reference materials with the value of the absolute thermo-emf. reference material (R. Tangas, Physics and Chenustry of Liguiols, 2, No. 1, 1970).

However, there is no standard, absolute thermo-emf. The material of which is known with high accuracy in a wide range of temperatures. Therefore, in the case of a small (on the order of units of microvolts per degree) absolute thermo - emf. The material under study remains debatable even the question of the sign of absolute thermo-emf.

The proposed method makes it possible, directly, i.e., without using a reference material, to determine the sign of the absolute thermo-emf of the material under investigation in a wide temperature range.

To this end, electrical conductors are connected with a conductor made of the material under study and a temperature difference is created between them. The direction of the temperature field between the containers is determined and disconnected. After the containers are disconnected, their temperatures are equalized and the direction of the electric field between them is determined. He compared the direction of the electric field with the direction of the temperature field at the moment of disconnection of the tanks, they determine the sign of the absolute thermo-emf. the studied material.

For example, a conductor is made of a capacitor plate of a large capacitance from the material under study. The plates are heated to

different temperatures, as a result of which the directional drift of charge carriers begins in the test material. In the case of only metallic conductivity, the electrons drift from the more heated plate to the less heated one. At very low temperatures, due to the phonon drag, the direction of electron drift may be reversed. Drift of charge carriers leads to the appearance of an electric field in space

between the capacitor plates.

The material to be examined is disconnected from the capacitor thus charged. The cores of the capacitor plates are aligned and electrometric are attached to them.

microvoltmeter. By the polarity of the voltage indicated by the microvoltmeter, the direction of the electric field in the space between the capacitor plates is determined. If nlastina, being less heated at the moment

disconnecting the material from the condenser, is charged more negatively, then the sign of the absolute thermo-emf. the test material is negative. If the capacitor plate is more negatively charged by another, then the material under study has a positive absolute thermo-emf.

Subject invention

The method of determining the sign of the small absolute thermo-emf. metals and alloys, which is based on the fact that, in order to directly determine the sign of thermo-emf. In a wide range of temperatures, electrical capacitances are connected with a conductor from the material under study, the temperature difference between them is created, and after the containers are disconnected, their temperatures are equalized and the direction of the electric field between them is compared with the direction of the temperature field at the moment of disconnection of the containers.