Microstrains in La1.85Sr0.15Cu1−yMyO4 (M=Zn, Ni, Mg) cuprates with y≤0.30

La1.85Sr0.15Cu1-yMyO4 ceramic cuprates with M = Zn, Ni, Mg, and y less than or equal to 0.30 have been synthesized. The superconcducting critical temperatures and the room temperature resistivities for M doping have been determined by a standard four-probe method. The width of each reflection of X-ray diffraction for each sample is analyzed by Rietveld refinements which is related to the average grain size and the average lattice microstrain. In this way we attempt to explain the stronger suppression for non-magnetic doping such as Zn or Mg than that for magnetic doping such as Ni. (C) 1998 Elsevier Science B.V.