89 research outputs found
Synthesis and Characterization of Nanocrystalline (Zrâ.ââYâ.ââ)Oâ.ââ-(Ceâ.ââ Smâ.ââ )Oâ.âââ Heterophase Thin Films
A new type of nanocrystalline samarium-doped-ceria/yttrium-stabilized-zirconia (SDC/YSZ) heterophase thin film electrolytes was synthesized on MgO and Si substrates by spin coating and thermal treatment of SDC-nanoparticle-incorporated polymeric precursors. In the heterophase films, SDC nanoparticles were uniformly dispersed in a nanocrystalline YSZ matrix. The heterophase structure was stable when fired in air at temperatures up to 850 °C. The nanocrystalline heterophase thin films exhibited electrical conductivities significantly higher than that of the phase-pure YSZ and SDC nanocrystalline thin films at reduced temperatures. The effects of SDC grain size and volume fraction on the electrical conductivity of the heterophase films were also studied
Magnetodielectric effect of Bi6Fe2Ti3O18 film under an ultra-low magnetic field
Good quality and fine grain Bi6Fe2Ti3O18 magnetic ferroelectric films with
single-phase layered perovskite structure have been successfully prepared via
metal organic decomposition (MOD) method. Results of low-temperature
magnetocapacitance measurements reveal that an ultra-low magnetic field of 10
Oe can produce a nontrivial magnetodielectric (MD) response in
zero-field-cooling condition, and the relative variation of dielectric
constants in magnetic field is positive, i.e., MD=0.05, when T<55K, but
negative with a maximum of MD=-0.14 when 55K<T<190K. The magnetodielectric
effect appears a sign change at 55K, which is due to transition from
antiferromagnetic to weak ferromagnetic; and vanishes abruptly around 190K,
which is thought to be associated with order-disorder transition of iron ion at
B site of perovskite structures. The ultra-low-field magnetodielectric
behaviour of Bi6Fe2Ti3O18 film has been discussed in the light of
quasi-two-dimension unique nature of local spin order in ferroelectric film.
Our results allow expectation on low-cost applications of detectors and
switches for extremely weak magnetic fields in a wide temperature range
55K-190K.Comment: 10 pages 4 figures, planned to submit to J. Phys.: Condensed Matte
Tuning dielectric properties in ceramics with anisotropic grain structure: The effect of sintering temperature on BaLa4Ti4O15
The orientation and grain aspect ratio, size and distribution of BaLa4Ti4O15 (BLT) ceramics have been studied as a function of sintering temperature with a view to elucidating a general principle by which the microwave properties (MW) can be understood/tuned in systems which exhibit anisotropic grain structures. For BLT sintered at 1500 °C, Δr reaches a maximum of 51, with tan ÎŽ minimum at 0.002 and ÏΔr = â 17 ppm/°C but Δr subsequently varies non-linearly as sintering temperature increases. Since Δr and ÏΔr are directly proportional in the absence of a phase transition, the variation of ÏΔr as a function of the sintering temperature is also nonlinear. This behaviour is related with variations in the orientation and grain aspect ratio, size and distribution with the sintering temperature and it is demonstrated that by controlling sintering conditions, microwave dielectric properties can be tuned. It is proposed that this is a general phenomenon which can also be used to explain the variation and tune the properties of other ceramic systems with anisotropic grain structures
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