Ferroelectric properties of strontium barium niobate crystals doped with rare-earth metals

The influence of doping of the SrxBa1 - xNb2O6 (x = 0.61) crystals (SBN-0.61) by rare-earth element (RE) dopants has been investigated. Taking into account the data available in the literature, it is demonstrated that the introduction of all rare-earth metals is accompanied by a substantial decrease in the temperature of the phase transition T-p and an increase in its smearing. The shift in the T-p temperature for certain rare-earth metals ranges up to 20 K per atomic percent of dopant in the crystal. It is experimentally established that, in the SBN-0.61 : Yb, SBN-0.61 : Ce, SBN-0.61 : Tm, SBN-0.61 : La, and SBN-0.61 : (Ce + La) crystals, a decrease in T-p brings about a considerable increase in the permittivity and the piezoelectric and electrooptical coefficients. The conclusion is drawn that the doping by rare-earth metals provides a means of optimizing the properties of strontium barium niobates. The pulse switching of the SBN-0.61 and SBN-0.61 : RE crystals is studied for the first time. It is found that the switching is characterized by a number of features, the most important of which is a decrease in the switched charge after the application of external fields. This effect associated with the specific features of the switching in the relaxor ferroelectric is assumed to be responsible for the instability of the parameters for strontium barium niobate material. (C) 2000 MAIK "Nauka/Interperiodica".