Observation of twin boundary layers in pure and alloyed YBa2Cu3O7-δ.

Using an electron diffraction technique, the thicknesses of the (nonorthorhombic) twin boundary layers were measured for pure and alloyed YBa2(Cu1-xMx)3O7-δ. Boundary thickness varied from ∼0.7 nm for M=Ni, x=0.02, and δ[bar_over_tilde:_approx._equal_to]0 to ∼2.6 nm for M=Al, x=0.02, and δ[bar_over_tilde:_approx._equal_to]0, while it was ∼1.0 nm for a pure YBa2Cu3O7. High-resolution transmission electron imaging of similar specimens supports the existence of such twin boundary layers. [ABSTRACT FROM AUTHOR]