In situ temperature measurement in the pressure chamber of diamond anvil cell.

The measurements of temperature directly influence the reasonability of experiments at high pressure and high temperature. In this article, we proposed a new integration design, the built-in thermocouple, for in situ temperature measurements in high-pressure-high-temperature experiments by fusing the characteristics of thermocouples and diamond anvil cells together. By integrating an S-type thermocouple inside the gasket of a diamond anvil cell, we successfully measured the temperature of the sample straight inside the pressure chamber at high pressure and high temperature. The setup underwent multiple experimental tests using internal and external heating techniques, the results of which revealed its capability to directly characterize the temperature of the sample with comparable accuracy and reliability to that of the typical external thermocouple setup. The proposed setup has also resolved the issue of the discrepancy of temperatures inside and outside the sample chamber and enormously expedited the temperature measurements by significantly reducing the response time of the thermocouple. In conclusion, the built-in thermocouple is a promising approach toward high-efficiency, in situ temperature measurements under extreme conditions.

Sample heating above 1400 K in a diamond anvil cell.

In high-pressure experimental methods, sample heating in the pressure chamber of a diamond anvil cell is an important topic, and numerous efforts have been made to improve and develop new technologies. In this paper, we propose a new type of internal resistance heating technique, the composite heating gasket, prepared by integrating an annular heater into the sample chamber for direct heating of the sample. As the effective heating area covers the entire pressure chamber wall, a relatively quasi-uniform temperature field is formed within the sample chamber. At the same time, the integration design reduces the risk of diamond oxidation and enables direct measurement of the spectroscopic properties of samples at high temperatures. The preparation of the composite heating gasket is simple and repeatable, and its heating performance is stable at temperatures above 1400 K. When the sample diameter is 210 µm and no thermal insulation is used, the diameter of the temperature zone in which the temperature difference is less than 10 and 20 K exceeds 120 and 170 µm, respectively. The composite heating gasket represents a significant advancement in providing a uniform temperature field for in situ measurements with diamond anvil cells at high pressure and temperature.