Ferroelastic twins in these ceramics were investigated by using transmission electron microscopy. It was found that, in all 3 materials, (100) twin formation was favored over (110) twin formation. In order to confirm the predominance of (100) twins, strain tensors were calculated for the 2 twins. The calculations demonstrated that (100) twins relieved more of the inherent strain in a twinned grain than did (110) twins. It was observed that, in going from LaAlO3 to NdAlO3, the twin shape changed from wedge to lamellar and the twin width decreased for a given grain. These features were attributed to an increased lattice distortion in going from LaAlO3 to NdAlO3.

Twin Structures in Lanthanum, Praseodymium and Neodymium Aluminate Ceramics. C.H.Kim, S.Y.Cho, I.T.Kim, W.J.Cho, K.S.Hong: Materials Research Bulletin, 2001, 36[9], 1561-71