Twin structures in lanthanum, praseodymium, and neodymium aluminate ceramics

Ferroelastic twins in LaAlO3 (LAO), PrAlO3 (PAO), and NdAlO3 (NAO) ceramics were investigated using transmission electron microscopy. In all three materials, (100) twin formation was favored over (110) twins. To confirm the predominance of (100) twins, strain tensors for the two twins were calculated. These calculations demonstrated that (100) twins relieve more strain inherent in the twinned grain than (110) twins. It was observed that, from LAO to NAO, the twin shape was changed from wedge to lamellar, and that the twin width was decreased for a given grain. These results were attributed to the increased lattice distortion from LAO to NAO.