True tolerance factor effects in Ln(1.85)(3+)M(0.15)(2+)CuO(4) superconductors

A series of seven Ln(1.85)(3+)M(0.15)(2+)CuO(4) samples has been prepared i n which mixtures of Ln = La and Nd and M = Ca, Sr, and Ba are used to incre ase the average radius from 1.180 to 1.223 Angstrom (equivalent to an incre ase of tolerance factor from 0.856 to 0.871) while the size variance is fix ed at a constant value of sigma (2) = 0.0020 Angstrom (2). X-ray powder dif fraction is used to study structural changes, and ac magnetic susceptibilit y, electrical resistivity, and thermoelectric power measurements show the v ariation of physical properties as a true function of the tolerance factor. (C) 2000 Academic Press.