Synthesis of New Pb-Based 1222 Cuprates Containing Phosphorus, (Pb0.75P0.25)Sr2(RE2-x-yCexSry)Cu2Oz(RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y)

New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb0.75P0.25)Sr-2- (RE2-x-y Ce (x) Sr (y) )Cu2O (z) (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single phase samples are obtained for 0.5a parts per thousand currency signxa parts per thousand currency sign1.0 and y=0.1 in the cases of RE = Nd, Dy, Ho, Er, Tm, Yb and Y, while for 0.3a parts per thousand currency signxa parts per thousand currency sign1.0 and y=0.1 in the cases of RE = Sm, Eu and Gd. The samples crystallize in a tetragonal lattice, the lattice parameters a and c are decreasing with the decrease of the ionic radius of the RE element. Even after annealing under 143 atm O-2 atmosphere at 400 A degrees C, almost all the samples with the common values x=0.5 and y=0.1 are semiconductors with a transport process followed by three-dimensional variable range hopping. However, the samples of RE = Sm, Eu and Gd, which are of almost single 1222 phase, even for x=0.3 and y=0.1, show superconductivity with the onsets at about 25 K, 20 K and 22 K, respectively. Through this study, we find very important procedure for discovery of new superconducting 1222 compound.