It was shown that the aliovalent substitution of sodium ions for Sr or Ba 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 Na concentration. The variation of c lattice parameter with sodium concentration was 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 sub-mm region. Simultaneously, rise of the ferroelectric phase transition temperature was observed with increasing sodium concentration.

Effect of Vacancies on the Structural and Relaxor Properties of (Sr,Ba,Na)Nb2O6. A.Belous, O.Vyunov, D.Mishchuk, S.Kamba, D.Nuzhnyy: Journal of Applied Physics, 2007, 102[1], 014111