Investigations of nano-crystalline Sr0.5Ba0.5Nb2O6 and Bulk Ceramics Synthesized by a Polymerization Method Using PEG400

Roberto Köferstein, Florian Oehler, Stefan Ebbinghaus
2018 Social Science Research Network  
Nano-crystalline Sr 0.5 Ba 0.5 Nb 2 O 6 was synthesized by a one-pot method using PEG400 and citric acid. Calcination of the (Sr,Ba,Nb)-gel at 600 °C leads to Sr 0.5 Ba 0.5 Nb 2 O 6 with a crystallite size of 24(2) nm and a specific surface area of 38.5(10) m 2 g 1 . Sintering up to 1325 °C leads to ceramics with globular or irregular-shaped grains and average grain sizes between 1.3 and 2.4 µm, whereas higher temperatures lead to a rod-like microstructure. The indirect allowed optical band
more » ... varies between 3.70(5) and 3.29(5) eV. Dielectric measurements show a diffuse phase transition and weak relaxor properties. The maximum of the permittivity occurs between 116 and 147 °C. The frequency dependence of the impedance can be well described by one or two RC-circuits depending on sintering temperature. The 2 melting temperature is determined as 1506(7) °C with H f = 140(20) kJ mol 1 . The average linear thermal expansion coefficient is found to be 10.5(5)10 6 K 1 .
doi:10.2139/ssrn.3410773 fatcat:6ffjxkmrvjfg3eia663eitw234