Microstructures of Zn,Ni,Mg doped La1.85Sr0.15CuO4 in high doping level

We successfully synthesized La1.85Sr0.15Cu1-xMxOy (M = Zn, Ni, Mg) with y l ess than or equal to 0.30 ceramic cuprates. X-ray diffraction studies show that there is no impurity phase in all Zn,Ni,Mg-doped LSCO. Rietveld refine ment technique is used to obtain the lattice constant,atomic position coord inates and reflection profile parameters for all samples. There is a tetrag onal-to-orthorhombic phase transition in the range of 0.10< y<0.20 for Zn-d oped samples. No phase ransition occurs in Ni and Mg-doped LSCO in the whol e doping range in the accuracy of our experiments. There is a jump in latti ce parameter c for Zn and Mg-doped LSCO in the same doping range from y = 0 .10 to y = 0.20, the relative change of atomic coordination of z for La(Sr) in La-site and O in O(2) site also has a jump in Zn or Mg-doped samples in the same doping range. The former may be due to the occurrence of T-O Phas e transition, and the latter may be due to the relative movement of atoms i n the unit cell. This may indicate that there may exist a phase transition or large lattice microstrain. The fitted atomic parameters for Ni-doped sam ples vary monotonically. In the assumption of Cauchy relation between machi ne broadening and physical broadening, the physical broadening of each refl ection for each sample is obtained. In this way, we calculated the average microstrains for Zn, Ni and Mg-doped samples. The variation of delta has a jump in Zn or Mg-doped samples while delta vary monotonically in Ni-doped s amples. The jump may be related to the relative movements of each atom in t he unit cell. This result is consistent with those obtained from the change of lattice parameters. The large changes of lattice parameters, relative a tomic positions and microstrains may be related to the suppression of T-c o f the samples in superconducting state.