A review is given of fixed points for pressure calibrations primarily related to semiconductor-to-metal transitions.
Effects of pressure environment and sample purity are discussed.

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The national primary standards in hydrostatic pressure range, about 1 Pa to 1.5GPa are described. The mercury column manometer is interferometric to measure pressures to 120kPa with accuracy of 0.5Pa. The dead-weight piston gauges are several for pressure range from 100kPa to 1.5GPa.
In order to assure the traceability of pressure scale, international comparisons are carried in cooperation with many countries. Domestically the government inspect the working standards used in laboratories and industries in accordance with the measurement law.
The pressure unit, Pa of SI was introduced into the legal units in 1966 but still not used in industry in Japan.

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Sintered diamond (SD) as the material of an anvil can generate pressure much higher than WC-Co. Three types of methods using SD anvils are described: “6-2 type” system in which a pair of Bridgman anvils are embedded in an octahedral cell of a cubic press, Drickamer cell, and “6-8 type” system in which the second-stage eight anvils are compressed by the first-stage six anvils. By using them, the simultaneous performance of the resistance measurement and X-ray diffraction at room temperature, the electrical detection of the superconducting transition at low temperature and X-ray diffraction at high temperature were carried out, respectively. Pressure calibration was made by the use of α→ε transition pressure in Fe-V alloys, the superconducting transition temperature as a function of pressure in Pb, or the lattice parameter of NaCl or Au. As a strong X-ray can pass through SD with Co binder, X-ray diffraction experiment is possible for the press geometry in which it is impossible for WC-Co anvil.

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Methods of the pressure and temperature measurement in diamond anvil experiments are described. In mega bar region, most reliable method for pressure measurement at present is an in situ x-ray diffraction study using synchrotron radiation. Pressure is calculated from the equation of state of a standard material such as gold and an example of experiment at 216 GPa is described.
In high pressure and high temperature experiment, by measuring the peak position and the line width of the ruby fluorescence line, both pressure and temperature can be determined simultaneously. This method, however, can be used only in the pure hydrostatic environment. Under nonhydrostatic condition, similar method can be used by using two standard material such as ruby and Sm doped YAG. Temperature dependence of the wavelength of Sm: YAG is very small and it is easy to determine the pressure even when the temperature is not known at all.
Temperature of the sample during laser heating can be determined from the emitted spectrum from the sample. When the measurement is made in a proper range of the wavelength, reliable temperature can be obtained even when the pressure dependence of emissivity is unknown.

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This paper reviews and discusses various assumptions which are employed in the analysis of shock compression data. Some of the assumptions are essential and strongly affect the determination of shock pressures and shock temperatures, but are often ignored; one is the jump condition and the situation of the steady flow, and another is the behavior of the Gruneisen constant which depends on the state of materials under shock loading. Furthermore, shock waves induce the heterogeneous state of materials shock-compressed, localizing thermal energy; it becomes difficult to compare with a single equation of state of solids.

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Pressure and temperature measurements in a belt-type high pressure apparatus were reviewed based on the publications by the General Electric Company. Their method is to calibrate pressure and temperature using the melting points or phase transitions of substances which have previously been determined. On the other hand, in the industrial process of material synthesis, pressure and temperature are routinely controlled by primary oil pressure and electric heating power, respectively, based on these calibration for particular sample assembly configurations.

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Compact self-clamping piston cylinder high pressure cells are described which allow the measurements of electrical resistivity, AC magnetic susceptibility and magnetic moment under pressures and at temperatures from 300K to liquid helium temperatures. Special efforts are made for the accurate determination of temperature of the sample and pressure generated in the sample region. Details of the technique and procedure are discussed for the temperature measurement using the thermocouple and Ge (carbon) thermometer and for the pressure calibration using the manganin wire gauge and the superconducting manometer.

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Methods of pressure and temperature mesurement are reported in a high pressure experiment at low temperature. Cubic-anvil and pitston-cylinder devises are used, in which load is kept constant during changing temperature in order a sample to keep constant pressure, though it is impossible to keep constant pressure in ordinary clamp type devise during changing temperature. Pressures are measured by using some materials which show phase transitions under pressure. Electrical resistivities of Sn, Bi and Hg and volume change of NH₄F are measured at 295K up to IOGPa, and pressure versus load curves are obtained. At low temperature pressures are determined by measuring pressure dependence of superconducting transition temperatures of Bi. Temperatures are measured by Pt-Co thermometer fixed outside a high pressure cell.

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It is desirable that many kinds of pressure manometers utilized at low temperature are developed, because under high pressure and low temperature it is somewhat troublesome to carry out different kinds of measurements at the same time.
There are two pressure scales available determining pressure at low temperature. The one is the NaCl-pressure scale and the other is the ruby-pressure scale. In the case of the electrical measurements, it is convenient to utilize the pressure dependence of the T_c of the standard materials. In section 2, the T_c(P)-dependence of the Bi (V) phase as a function of pressure determined by the ruby-pressure scale is described. In section 3, experimental setup of some high pressure cell for electrical resistance measurement are described.

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Diamond anvil cells for the spectroscopic experiments at low temperatures are briefly reviewed. The techniques developed recently to obtain hydrostatic pressure and the method to calibrate the pressure are described. A description is also presented about the cryogenic optical systems designed by the authors to use for the high-field magneto-optical measurements of materials under high pressure.

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