PREPARATION, CRYSTAL STRUCTURE, AND DIELECTRIC PROPERTIES OF NEW SOLID SOLUTIONS (Pb1–2xWx)O1+x (x ≈ 0.05) BASED ON THE TETRAGONAL FORM OF LEAD OXIDE

Single crystal X-ray diffraction (XRD), thermogravimetric, and dielectric studies are performed for single and polycrystalline samples of [(1– x )PbO + x WO 3 ], 0≤ x ≤0.20, synthesized by solid phase reactions and crystallization of melts. The formation of previously unknown solid solutions based on the tetragonal form of lead oxide (α-PbO) – Pb 1–2 x W x O 1+ x , x ≈ 0.05 is observed. Single crystals of solid solutions are analyzed by XRD at 100 K and 293 K. It is found that their crystal structure isotypical to α-PbO is characterized by the orthorhombic space group Cmma with unit cell parameters (293 K) a = 5.510 Å, b = 5.570 Å, c = 5.301 Å. The main structural characteristics of solid solutions are determined. A structural model of the formation of solid solutions is established, according to which partial W substitution for Pb in α-PbO is accompanied by the inclusion of additional oxygen atoms to the location of lone pairs of substituted Pb 2+ and the formation of vacancies in this cation sublattice. Temperature dependences of the permittivity and losses of solid solution crystals studied in the temperature range T = 80-570 K and at frequencies f = 1-1000 kHz do not have features characteristic of phase transitions.