At low temperatures the compounds Bi2WO6 and Bi2MoO6, like many other related layered ferro‐electrics, are electrically polar and transform to nonpolar state on heating. These phase transitions, however, are not ordinary ferroelectric ones and have a reconstructive nature. The two compounds undergo also additional phase transitions which are not accompanied with any noticeable changes in structure or polarization. Some physical properties of Bi2WO6 single crystals and Bi2MoO6 ceramics are studied and discussed.

Crystals of KTiOPO4, RbTiOPO4, and TlTiOPO4 are grown, studied, and found to be ferroelectrics with Curie points of 934, 789, and 581 °C, respectively. The phase transitions are of displacive type and nearly of second order. These crystals have also a high ionic conductivity and can exhibit a strong low‐frequency dielectric relaxation.

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X-ray photoemission spectroscopy (XPS) measurements have been executed for TlTiOPO 4 to elucidate the general features in the electronic structure of the KTiOPO 4 family compounds. The peculiarities of the valence band structure have been discussed for the crystals. The persistence of core level binding energy differences O 1s–P 2p and O 1s–Ti 2p 3/2 has been detected in TlTiOPO 4 and KTiOPO 4, which relates well with the constancy of averaged P – O and Ti – O chemical bond lengths in this crystal family. The superstructure ordering of the TlTiOPO 4 surface subjected to polishing and annealing has been detected by reflectance high energy electron diffraction (RHEED). From comparison of surface crystallographic properties of TlTiOPO 4 and KTiOPO 4, the most typical superstructure indices have been revealed.

Single crystals and polycrystalline Bi2WO6 samples are used to measure the dielectric constant, loss, and electrical conductivity, over a wide range of temperature, oxygen partial pressure in ambient atmosphere, and frequency of the measuring electric field. Maxima of the dielectric constant are observed at phase transitions close to 930 and 960°C. The Curie constant for bismuth tungstate is 1.4 × 105 K, the Curie‐Weiss temperature is equal to 926°C. The electrical conductivity of Bi2WO6 in the range 400 to 700°C is practically purely ionic at oxygen partial pressures of 1 to 10−1 atm, and electronic at PO2 = 10−2 to 10−5 atm. The maxima in the dielectric constant and tan δ in the range from 400 to 700°C, as the investigations of their frequency dispersion and the dependence on the composition of the ambient atmosphere revealed, have a relaxation character and are connected with the formation of two types of defect associates in crystals. The possible nature of crystal lattice defects responsible for electrical conductivity and relaxation phenomena is discussed.