However, twinning is commonly observed in LaA103 crystals.
It has been found that (100) is an active twin plane in LaA103 [73].
This twinning results in a rough crystal surface, strain and non-isotropic microwave properties
for (001) LaA103 wafers. To overcome the twinning problem, a new twin-free
substrate, Lao.gSro.7Alo.65Tao.3509 (LSAT), has been developed, which is a solid
solution of LaA103 and Sr2A1TaO6 [74, 75].
The dielectric constant and thermal
expansion coefficient of LSAT are comparable to those of LaA103 as seen from
Table 5.1.