SU940025A1 - Device for determination phase transition temperatures - Google Patents

Description

(54) DEVICE FOR DETERMINING TEMPERATURES OF PHASE TRANSFORMATIONS

one

The invention relates to a measurement technique, mainly a technique intended for the investigation of semiconductor materials, and can be used in determining the temperature of phase transformations in semiconductors, metallic alloys, ferroelectrics and other solids.

A device is known for determining the temperature of phase transformations by their thermal effect, comprising a heating, Q furnace and a thermocouple for measuring the temperature of the test substance 1.

However, the known device is not sensitive enough in temperature measurement.

The closest technical solution to the present invention is a device for determining temperature 15 of phase transformations in solids, comprising a dielectric case in which a heater is located, a thermocouple with a meter and an EMF indicator connected to it, and a detector of phase transformation heat 2.

In the known device, the phase transformation temperature is determined by measuring the temperature of the test substance with a thermocouple and fixing the moment of conversion in the appearance of the EMF at the output of the differential thermocouple, due to the occurrence of a temperature difference between the reference and the test substance due to the release or absorption of the heat of transformation in the latter. The sensitivity of the known device is limited by the ability of the differential thermocouple to detect small temperature differences between the sample and the standard, i.e. its differential thermal emf coefficient.

The purpose of the invention is to increase the sensitivity of the device.

To achieve this goal, a device for determining phase transformation temperatures in solids, containing a dielectric case in which a heater is located, a thermocouple with a meter and an EMF indicator connected to it and a phase transformation heat detector, is made in the form of two semiconductor plates of different conductivity type thin-film ohmic contacts on both sides, while on one side of the plates brought into contact with the test solid, ohmic co The contacts are interconnected, and the ohmic contacts on the other sides of the plates are connected to the EMF indicator.

FIG. 1 schematically shows a device, a general view; in fig. 2 - the same, longitudinal section; in fig. 3 - recording the recorder, when the structure is heated from 195 to 210 ° K.

The device consists of a heater 1, a thermonar 2 with an EMF meter 3 connected to it, an EMF indicator 4 connected to a phase change detector 5 located in a dielectric case 6. On base 7, one semiconductor plate 8 is fixed and a movable cover 9 to which a second semiconductor plate is attached 10. The test sample 11 is placed between the plates and moving the movable flap is clamped between the semiconductor plates until thermal contact forms between the sample and the plates. A thermocouple layer 2 is pressed against the sample. The case is placed in a furnace and, by heating or cooling the gro, the EMF is measured between the external contacts of the semiconductor wafers. With slow heating or cooling, the temperature of the sample and semiconductor wafers are almost the same and the temperature gradient in them is absent, as a result of which the emf at the output is zero. At the time of phase transformation in the sample, the heat of transformation is absorbed, which leads to the appearance of a temperature difference between the inner and outer sides of the semiconductor wafers and the appearance in them of a thermal thermal emf. Since the volume thermo-emf is opposite in semiconductors of various types of conductivity, they are summed when the internal ohmic contacts are connected, and a voltage appears between the external contacts, the maximum of which corresponds to the phase transformation moment. The magnitude of the output signal is much larger than in the known device, due to the large values of the differential emf of semiconductor materials.

The device is used, for example, to determine the temperature of the structural phase transformation in 5p crystals (1p-OeoDe. The thermal conversion effect detector is assembled from two plane-parallel silicon wafers of a conductivity type (carrier concentration 10) with dimensions of 6 X 6 X 0.5 m. One of plates attached to the fixed part of the body

from organic glass, others to the moving part of the same body. On both sides of the semiconductor wafers, thin-film ohmic contacts are applied, to which silver wires are soldered. The test sample in the form of a rectangular plate 6 X 6 X I mm is placed in the space between the red plates and clamped by moving the movable part of the dielectric body. To register the temperature of the sample in the fixed part of the body, a copper-constantan thermocouple is mounted. The heating of the system is carried out by passing an electric current through the windings of the furnace heater. To reach temperatures below room temperature, the device is placed in a cryostat with liquid nitrogen.

Signal from silicon wafers (J is fed to the input of a TR-1452 microvoltmeter, and from a microvoltmeter output - to the Y terminal of a two-coordinate self-recorder. The recorder's X terminal receives a signal from a copper-constantan thermocouple recording the sample temperature. Us2400 mV thermocouple signal, which corresponds to a sample temperature of 203 ° K, a peak is clearly distinguished due to the phase transformation of the first kind.

Claims (2)

1. Berg L., Introduction to thermography. M. Publishing House of the Academy of Sciences of the USSR, 1961, p. 7-11. 2.Schultre D.Differentialthermoanaiysi, Verlag der Wissenschaften. Berlin, 1969, s. 21 (prototype). FIG. U, juS go w IHVTSMvIA) v " ffffff 2500 gcho gooo (r, JuB 5