  Binary post-asymptotic giant branch (post-AGB) stars are products of a poorly
understood binary interaction process that occurs during the AGB phase. These
systems comprise of a post-AGB primary star, a main-sequence secondary
companion and a stable circumbinary disc. Studying the structure and properties
of these circumbinary discs is crucial for gaining insight into the binary
interaction process that governs post-AGB binaries as well as comprehending the
disc's creation, evolution, and its interaction with the post-AGB binary
system. We aim to use near-infrared polarimetric imaging to investigate the
morphology and potential substructures of circumbinary discs around eight
representative post-AGB binary stars. To achieve this, we performed
polarimetric differential imaging in H and Y bands using the high-angular
resolution capabilities of the European Southern Observatory-Very Large
Telescope/SPHERE-Infra-Red Dual-beam Imaging and Spectroscopy instrument. We
resolved the extended circumbinary disc structure for a diverse sample of eight
post-AGB binary systems. Our analysis provided the first estimates of the disc
scale-height for two of the systems: IW Car and IRAS 15469-5311. We also
investigated the morphological differences between the full discs (with the
inner rim at the dust sublimation radius) and transition discs (which are
expected to have larger inner cavities), as well as similarities to
protoplanetary disks around young stellar objects. We found that the transition
discs displayed a more intricate and asymmetric configuration. Surprisingly, no
correlation was found between the over-resolved flux in near-IR interferometric
data and the polarimetric observations, suggesting that scattering of light on
the disc surface may not be the primary cause of the observed over-resolved
flux component.
