Influence of thermal
prehistory on the electrical properties of tungstate
crystals
Chem.
Met. Alloys 4
(2011) 72-76
https://doi.org/10.30970/cma4.0161
V.N. SHEVCHUK, I.V. KAYUN
Temperature- and time-induced
changes of electric and dielectric parameters of AWO4 (A =
Cd, or Pb) single crystals
were studied experimentally. The dielectric properties measured along the [001]
direction in PbWO4 single crystals (scheelite
structure type) show a quasi-periodicity at about 20 h of free relaxation.
A connection of this quasi-periodicity with structural and point defects
dynamics, their interactions and the creation/rebuilding of complex defects
(duration of the relaxation processes), is proposed. The main role in these
phenomena is attributed to oxygen and lead vacancies. No thermodielectric
effects were observed for CdWO4 (wolframite
structure type) perpendicular to the cleavage face (010) up to 500 K.
Perspective view of the
crystallographic unit cells of PbWO4 (a) and CdWO4 (b).
Some elements of the structure are presented inside the unit cells. The hkl-indexes label the corresponding slip
planes. The intersections of the planes are depicted by the AB, AC, and AD
lines. The external electric dc field was applied parallel to the vector E.
Keywords
Tungstate crystal / Dielectric properties /
Lattice defects / Relaxation