Texture determination of the high temperature superconductors by emission Mössbauer spectroscopy

A method using emission Mössbauer spectroscopy has been developed for determining the degree of texture of bulk samples of high temperature superconducting ceramics having axial type of texture. A special fitting procedure was used, which takes into account properties of the electric field gradient on the 57Co probe nucleus, based on expressions determining the probabilities of the quadrupole transitions assuming perfectly aligned crystallites [P. Boolchand et al., Phys. Rev. B 38, 11313 (1988)]. The deviation of the line intensity ratio of the measured spectrum from the value expected for 100% texture was taken into account by a reduction factor which is associated with the imperfectness of alignment [F. Hartmann‐Boutron and V. Gross, Physica C 172, 267 (1990)]. This factor can be used as a precise measure of c‐axis orientation regardless of the specific kind of orientation distribution of crystallites. The established correlation between the experimental value of the reduction factor and the characteristic parameters of different distribution functions permits us to compare the results of the texture determination by emission Mössbauer spectroscopy with those obtained from x‐ray or neutron diffraction measurements. The high degree of reproducibility of the experimentally determined texture attests to use of this relatively simple, convenient, and accurate technique for texture characterization of the high temperature superconductor ceramics.