Ferroelectric Transitions in SrxBa(1-x)Nb2O6 - Effect of Thermal History on the Functional Properties

Many functional materials used in todays electronic equipment have a high content lead. Due to the environmental challenges related to production and usage of such materials, extensive research has been preformed on lead-free alternatives. Strontium barium niobate (SBNX) is one of many material systems suitable for replacing the lead-based materials. Functional properties and crystal structure of SBN has in this study been investigated with respect to variations in thermal history. Samples of SBN30, SBN40 and SBN50 have been synthesized through the solid state route. Each composition has been heat treated for at least 12 hours at various temperatures, and subsequently characterized by powder X-ray diffraction (all compositions) and dielectric spectroscopy (only SBN40 and SBN50). The peak in dielectric permittivity is observed to shift towards lower temperatures for increased sintering temperature. For SBN40, the peak in dielectric permittivity shifted 100C due to an increase in sintering temperature from 1300C to 1400C. A transition from normal ferroelectric to relaxor behavior has been observed as a result of increasing sintering temperature. For samples sintered at 1350C and 1400C, increasing frequency caused both a dispersion of measured permittivities and a shift towards higher temperatures for the peak in dielectric permittivity. The crystal structure was also affected by the increasing sintering temperature. Both unit cell parameters show temperature dependent behavior, causing the unit cell volume to decrease as the sintering temperature increases