  The superconducting system La2-xBaxCuO4 is known to show a minimum in the
transition temperature, Tc, at x = 1/8 where maximal stripe order is pinned by
the anisotropy within the CuO2 planes that occurs in the
low-temperature-tetragonal (LTT) crystal structure. For x = 0.095, where Tc
reaches its maximum value of 32 K, there is a roughly coincident structural
transition to a phase that is very close to LTT. Here we present a neutron
scattering study of the structural transition, and demonstrate how features of
it correlate with anomalies in the magnetic susceptibility, electrical
resistivity, thermal conductivity, and thermoelectric power. We also present
measurements on a crystal with 1% Zn substituted for Cu, which reduces Tc to 17
K, enhances the spin stripe order, but has much less effect on the structural
transition. We make the case that the structural transition correlates with a
reduction of the Josephson coupling between the CuO2 layers, which interrupts
the growth of the superconducting order. We also discuss evidence for
two-dimensional superconducting fluctuations in the normal state, analyze the
effective magnetic moment per Zn impurity, and consider the significance of the
anomalous thermopower often reported in the stripe-ordered phase.
