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Ground State and the Metal-insulator Transition in (Pr1−yYy)1−xCaxCoO3 (0.45 ≤ x ≤ 0.55) Cobaltites
A. J. Bar´on-Gonz´alez,J. L. Garc´ıa-Mu˜noz,J. Herrero-Mart´ın,C. Frontera,G. Sub´ıas,J. Blasco 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Pr0.5Ca0.5CoO3 exhibits a non-conventional metal-insulator transition (MIT) in which the insulatingstate is due toa volume contraction (2%) and electron transfer from Pr to Co sites. Pr1−xCaxCoO3cobaltites with Ca doping around x 0.5 (0.45 ≤ x ≤ 0.55) have been investigated. Different ground states and phase transitions are reported in samples at both sides of the half-dopedcomposition. The relevance of the Pr/Ca ratio around half-doping and the amplitude of the changesobserved at the MIT are analyzed. Besides the expected variation in the transition temperature, wereport an enhanced Pr3+/Pr4+ transformation at the MIT in Pr0.45Y0.05Ca0.50CoO3[0.25(5) e−/Pr ion and TMI = 120 K] with respect to Pr0.5Ca0.5CoO3[0.15(5) e−/ Pr ion and TMI = 75 K].
Standardization of Fracture Toughness Testing of Ceramics in the United States
Quinn, G.D.,Jenkins, M.J.,Salem, J.,Bar-On, I. The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.4
American Society for Testing and Materials (ASTM) standard test method PS 070-97 has been created for measuring fracture toughness of advanced ceramics. PS 070-97 includes three test methods which use beams in bending: chevron notch (CNB), single-edged precracked beam (SEPB), and surface crack in flexure (SCF). Supporting data has been collected through several Versailles Advanced Materials and Standards round robins. This paper discusses the evolution of the standard including the rationale for the choice of the three methods and the specifications in the standard. Progress on Standard Reference material 2100 which will have certified values of fracture toughness is presented.