Abstract
A systematic study of the phase stability of La(Pr)
2−
x−
y
R
x
Sr(Ba, Ca)
y
CuO
4 (R = rare earth) compounds reveals a broad composition range for T*-phase formation. Several members of this series of compounds show bulk superconducting transition temperatures up to
T
c ∼ 20 K. These superconducting cuprates raise further questions about the relationship between structural stability and high temperature superconductivity in oxides.