Abstract
The crystal structures and domain textures of some tetragonal and hexagonal niobium and tungsten bronze type tunnel structures are reviewed. Only phases exhibiting ferroelectric/ferroelastic type behaviour are included. As well as ferroelectric and ferroelastic domains there are commensurate and incommensurate phases to be characterized, as well as non-stoichiometric effects due to partial filling on some pentagonal or hexagonal tunnel sites and mixed occupancy of the (Nb, W) octahedral sites.