• Infrared Spectroscopy Of Ba_3+y Co_1+xNb_2O_9 Ceramics

      Ibrahim, Samia; Department of Physics
      The dielectric properties of ceramic Ba3+y Co1+xNb2O9 where x= 0,-0.07,0.03 and y = 0, -0.03 were characterized because it might used for a wide range of applications including wireless communication used in mobile communication, ultra high speed local area networks, intelligent transport system and satellite communications. Room temperature optical re ectivity measurements of ceramics sintered at di erent temperatures between 1200 C to 1500 C were made covering the spectral range between 70-8000 cm􀀀1. The Lorentz model was used to t the re ectance data to make extrapolations for Kramers Kronig (K-K) analysis and to estimate the microwave properties. K -K analysis was applied to extract the other optical response functions from the re ectance data ( optical conductivity and dielectric permittivity). Powder X-Ray di raction measurements were done with 2 in the range between 10 to 80 degree for all samples. Most samples exhibit some degree of 1:2 ordering which appears as small superlattice peaks at 17.6 and 12 degree. All samples exhibit a small amount of impurity phases. The main purpose of this work is to study the e ect of the density, 1:2 ( Co:Nb) ordering and concentration of Cobalt on the dielectric properties. It was shown that density has a clear e ect on the dielectric properties. For example 1 (50 cm􀀀1) decreased if the densjhfnadfity decreased. On the other hand the change of the concentration of Cobalt does not have any real e ect on the dielectric properties. 1:2 order also has an e ect on the dielectric properties. It was observed that the scattering rate of the optical phonon was smaller in sample exhibiting more 1:2 order.