Praseodymium Substitution Research Articles

Increased T c of bismuth strontium calcium copper oxide superconductor by praseodymium substitution

It is shown that a small substitution of praseodymium for bismuth as in Pr0.05Bi1.95Sr2CaCu2.2O8.2+δ produces a significant increase, 13 K, in the onset temperature, 7 K in the temperature at which the whole specimen is superconducting, and 10 K in the transition-midpoint temperature relative to Bi2Sr2CaCu2.2O8.2+δ. Unfortunately the transition is broadened, 20 K versus 14 K. Doubling the amount of praseodymium substitution causes the occurrence of extraneous phase(s), the effect of which is seen only in the resistance versus temperature data, and does not indicate any additional significant increases in the aforementioned temperatures.

Magnetic Anisotropy and Spin Reorientation in Nd2-xPrxCo14B

ABSTRACTNd2-xPrxCo14B intermetallics crystallize in tetragonal form isostructural to Nd2Fe14B. Structural and magnetic properties of the polycrystalline materials have been determined. Room temperature magnetic measurements indicate that these intermetallics exhibit uniaxial anisotropy throughout the entire composition range. Substitution of praseodymium in Nd2-xPrxCo14B significantly enhances the anisotropy field both at 78 K and at room temperature. Magnetization versus temperature plots show spin reorientation TSR2 at 546 K for Nd2Co14B and at 668 K for Pr2Co14B. TSR2 increases linearly with composition x. The 3d sublattice anisotropy which seeks the tetragonal plane appears to dominate above these temperatures. In addition to the above, low temperature magnetic measurements demonstrate the spin reorientation in Nd2Co14B and Nd1.9Pr0.1Co14B. Further additions of praseodymium strengthen the axial anisotropy at temperatures down to 4.2 K. Effect of competing crystal field interactions and the consequences of praseodymium substitution that result in considerable increase in anisotropy field in these quaternaries are discussed.

Effects of Rare Earth Impurities on Photochromic Characteristics of Rare Earth Orthoniobates

Some rare earth orthoniobates, RNbO4, have been found to exhibit photochromic properties ascribed to the formation of color centers. Compounds with rare earths, R, of gadolinium and ytterbium, have been shown to have a particularly long duration of visible coloration after ultraviolet (UV) irradiation at room temperature. Partial substitution of praseodymium or terbium as the rare earths enhances these UV coloration characteristics. Substitution of about 0.8% of terbium is remarkably effective in accelerating the thermal bleaching, increasing the bleaching rate by about one order of magnitude.