Strontium–barium niobate single crystals, growth and ferroelectric properties

Single crystals of strontium–barium niobate SrxBa1−xNb2O6 (SBN) undoped and doped with Ce or Cr were grown by the Czochralski method. The inductive heating system was used. In order to improve conditions of growth, a crucible-base cooling was introduced. Single crystals of the following nominal compositions have been obtained: Sr0.4Ba0.6Nb2O6, Sr0.5Ba0.5Nb2O6, Sr0.61Ba0.39Nb2O6 (congruent melting) and Sr0.75Ba0.25Nb2O6, designated hereafter as SBN40, SBN50, SBN61 and SBN75. They were up to 22 mm in diameter and 40 mm in length with characteristic 24 faces, free from striations and other extended defects. All the crystals were grown in the [0 0 1] direction. The dopants (Ce or Cr) were added to the SBN61 composition. By use of ICP-OES method, the chemical compositions were checked. Etch pit density was also measured. In the case of the undoped single crystals, it was found to be 2.4×102–5.6×103 cm−2 but in the case of Ce or Cr doping, it increased up to 3.6×104–1.8×105 cm−2.Investigations of the linear dielectric response measured within 100⩽f⩽105 Hz along the polar c-axis of four obtained single-crystalline SBN compounds revealed a gradual crossover from conventional ferroelectric (SBN40) to extreme relaxor (SBN75) behavior.