Pressure-induced valence change in the rare earth metals; The Case of praseodymium

Tateiwa, Naoyuki; Nakagawa, Akitoshi*; Fujio, Kazuhiko*; Kawae, Tatsuya*; Takeda, Kazuyoshi*

Journal of Alloys and Compounds, 408-412, p.244 - 247, 2006/02

https://doi.org/10.1016/j.jallcom.2005.04.032

The rare earth metal praseodymium (Pr) transforms from the d-fcc crystal structure (Pr-III) to -U one (Pr-IV) at 20 GPa with a large volume collapse ( = 0.16), which is associated with the valence change of the Pr ion. The two 4f electrons in the Pr ion is supposed to be itinerant in the Pr-IV phase. In order to investigate the electronic state of the phase IV, we performed the high-pressure electrical resistance measurement using the diamond anvil cell up to 32 GPa. In the Pr-IV phase, the temperature dependence of the resistance shows an upward negative curvature, suggestting the narrow quasiparticle band of the 4f electrons near the Fermi energy. A new phase boundary is found at in the Pr-IV phase. From the temperature and magnetic field dependences of the resistance at 26 GPa, the ground state of the Pr-IV phase is suggested to be magnetic. Several possibilities for the origin of are discussed.

Development of Quality Assurance System for Resistance Welding by Ultrasonic Examination -Fabrication of STB for Resistance Welding and Ultrasonic Examination-

Kono, Shusaku; Seki, Masayuki; Fujio, Ishibashi,; Hirako, Kazuhiko*; Tsukada, Tatsuya*

JNC TN8430 2003-010, 28 Pages, 2003/07

JNC-TN8430-2003-010.pdf:2.18MB

The defect occurred at the resistance welding zone is very minute and therefore cannot be identified by X-ray inspection. Then, the ultrasonic examination method, in which the resolution of the defect is higher than that of the X-ray inspection method, has been developed. The ultrasonic wave sounds straight easier in the material than X rays, excels in defecting the micro defect. However, the pulse amplitude of ultrasonic wave is influenced by the shape and direction of the defect. Then, the ultrasonic inspection equipement, in which the ultrasonic probe and the sample rotation axis are controlled to drive with the pulse motor and the defect data (position and size)are analized by image processing ultrasonic signal, was developed to measure the shape and the position of defect accurately. However, an ultrasonic examination method is the comparative inspection method. Therefore, the standard test block or the reference block is indispensable to guarantee the defectability and the ultrasonic echo sensibility of the inspection device. The standard test block is provided in JIS etc, it is needed to defect the peculiar defect occurred at the resistance welding zone. Then, the method of processing a standard test block is examined, the standard test block was made experimentally by electric discharge processing and diffusion junction method. The ultrasonic echo sensitivity and the threshold for image processing were proofread by using the standard test block, the ultrasonic inspection and metallographic inspection were executed. Comparing the ultrasonic inspection results with the metallographic inspection results, the detectability of defect depth and the measurement accuracy were proved to be 3m and with errors less than 10m respectively. From these results, the effectireness of proofreading the ultrasonic inspection condition by the standard test block was confirmed. Moreover, it was confirmed that there was a peculiar relationship between the depth ...