Anomalous increase in the unipolarity of doped lithium niobate crystals inthe temperature range 300-400 K

The lithium niobate single crystals doped with B, Zn, and Gd at a content o f 0.002-0.44 wt % have been grown. Their domain structure, static and dynam ic piezoelectric properties, dielectric properties, and conductivity are in vestigated over a wide range of frequencies. The dielectric dispersion asso ciated with the Debye-type relaxation process and considerable anomalies in epsilon(22)'(T) and conductivity are revealed in the temperature range sim ilar to 300-400 K. At these temperatures, the piezoelectric modulus d(33) o f the initial polydomain crystals LiNbO3 : Gd jumpwise increases up to the values close to those for the undoped single-domain crystal. This increase is accompanied by a substantial change in the etch patterns due to the doma in structure of the crystal. The nature of the anomalies observed in LiNbO3 in the above temperature range is discussed. (C) 2000 MAIK "Nauka/Interper iodica".