Twin domains form during the second order structural phase transition between socalled

high symmetric tetragonal phases and low symmetric orthorhombic phases

in YBCOx (YBa2Cu3O6+x, 0 < x < 1). A new analytical approach to coherence

effects in diffraction from a twinned model of YBCOx sample was presented and it

was shown that, for a small mean width of the twin domains, and small strains,

coherence effects gave rise to extra peaks between {h00} reflections (central peak)

such that their intensity died away as the strain and the mean width of the twin

domain were increased. Therefore in diffraction studies of phase characterization

or lattice constants, the coherence effects must be taken into account. Researchers

who were interested in “structural phase transitions” involving reduction in crystal

symmetry may find it necessary to consider the “width of twin domains” as a new

kind of order parameter.

Coherence Effects of Twin Domains in Diffraction from High Tc YbCox.

B.Khoshnevisan: Physica C, 2008, 468[21], 2187-90