Effect of vacancies on the structural and relaxor properties of (Sr,Ba,Na)Nb2O6

It has been shown that the aliovalent substitution of sodium ions for strontium or barium ions in strontium barium niobate relaxor ferroelectric causes a decrease in vacancy content of the samples and a linear variation of unit cell volume with sodium concentration. The variation of c lattice parameter with sodium concentration is determined by deformations of the NbO6 oxygen octahedrons in the 001 direction. Dielectric studies carried out in a wide frequency range showed that the decrease in the vacancy content of the Sr0.6-xBa0.4Na2xNb2O6 and Sr0.6Ba0.4-yNa2yNb2O6 results in suppression of relaxor ferroelectric properties, which was manifested in both low-frequency and submillimeter region. Simultaneously, rise of the ferroelectric phase transition temperature was observed with increasing sodium concentration. (c) 2007 American Institute of Physics.