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Twin wall related diffuse scattering intensities from a single crystal of LaAlO3 were determined using high-resolution x-ray diffraction methods. Rocking curves were measured for sample temperatures between 295 and 900 K. The wall thickness W was determined by comparing the observed diffraction profiles with structure factor calculations for a tanh(x/W) wall profile. It is shown that W≈20 Å at low temperatures and increases slowly with temperature reaching values in excess of 200 Å near Tc≈850 K with W∝|T−Tc|−1.

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Weak uniaxial stress (< 1 kPa) along the cubic [100] and [110] directions of modifies significantly the domain structure near the crystal surface on cooling to the tetragonal phase. High-resolution x-ray rocking curves show that oriented slabs have a preference of `c' domains perpendicular to a small (001) surface. On heating from 10 K the domain population increasingly randomizes when the transition point is approached. In oriented slabs the domain population is more random with little temperature dependence for nominally stress-free samples. Uniaxial stress along increases the population of `a' domains for . The `c' domains have characteristically shorter length scales perpendicular to the surface than the larger `a' domains. The rocking angle of `c' domains has a much larger angular spread (ca ) than those of `a' domains.

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