Electric permittivity and conductivity of (Na0.5Pb0.5)(Mn0.5Nb0.5)O3 ceramics

• Published in: Solid state ionics Vol. 176; no. 15-16; pp. 1439 - 1447
• Main Authors: Molak, A., Ksepko, E., Gruszka, I., Ratuszna, A., Paluch, M., Ujma, Z.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-05-2005
• Subjects: Ceramics; Dielectric relaxation; Mixed electrical conductivity; Scanning electron microscopy (SEM); XRD; 61.16.B; 72.60; 78.20.C; Scanning electron microscopy (SEM); 81.05; 77.22.G; Ceramics; Mixed electrical conductivity; XRD; 61.10.N; Dielectric relaxation
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2005.03.013

The (Na0.5Pb0.5)(Nb0.5Mn0.5)O3 ceramics have been obtained from oxides by sintering in air, using a two-step process with precursor phase. Analysis of split lines in the XRD spectra allowed the determination of the crystallographic system of the solid solution, which consisted of one phase. The monoclinic space group P21/m was identified. Cell parameters are a=11.303(2) Å, b=11.536(2) Å, c=11.225(2) Å, β=88.71(2)°, V=1463.4(4) Å3. The high-value dielectric permittivity shows frequency dispersion in temperature characteristics. Electric modulus formalism distinguishes two relaxation processes. One is characterized with energy activation Eτ,A=0.36 eV and conductivity relaxation characteristic time τ0,A=1×10−12 s. The other with Eτ,B=0.42 eV and characteristic time τ0,B=2×10−11 s. They were attributed to oxygen ions jumping between vacancies VO or Mn–VO complexes. Ionic conductivity is postulated for high temperature. Variable range hopping (vrh) small polaron conductivity manifests below 220 K. Density of states at the Fermi level, N(EF) was estimated as 1.6×1019 eV−1 cm−3 using the vrh model.