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In this work, the effect of BaTiO3 (BT) addition on structural, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramic was investigated. Ceramic samples with the chemical formula (1-x)CaCu3Ti4O12 -xBaTiO3, (1-x)CCTO-xBT, (x = 0.00, 0.10, 0.20, 0.30, 0.50 and 1.00) were synthesized by solid state route. The structural studies carried out by X-ray diffraction technique and showed that the perovskite structure cubic and tetragonal phases were formed without any other impurity phases. The addition of BaTiO3 into CCTO system lowered the last crystallite size to about 52 nm and increased the dielectric constant by four orders compared to pure CCTO. Moreover, the results of the complex impedance analyses of (1-x)CCTO-xBT ceramics samples confirmed the presence of non-Debye type of relaxation phenomenon and exhibited a negative temperature coefficient of resistance behaviour.Keywords: Ceramics, Barium titanate, Raman spectroscopy. Chemistry; Vol. 29, No. 8 (2017), 1811-1816 a mixture CCTO and BaTiO3 characteristics. In the present work we are reporting the synthesis of (1-x)CCTO-xBT by solid state reaction route. The structural, dielectric and electrical properties of (1-x)CaCu3Ti4O12-xBaTiO3 ceramics (where x = 0.00-1.00) were investigated. Asian Journal of EXPERIMENTALThe (1-x)CCTO-(x)BT samples were synthesized by means of a conventional mixed oxide route. High-purity oxides and carbonates; CaCO 3 (99.8 %) CuO (purity, 99 %), TiO 2 (purity, 99.95 %) and BaCO 3 (purity 99.5 %) (All Sigma Aldrich chemicals, USA) were used as starting materials.Synthesis of (1-x)CaCu 3 Ti 4 O 12− − − − −xBaTiO 3 : The powders were weighed in stoichiometric proportion and milled for 1 h. Then the slurry was dried in an oven at 80 °C. The calcinations processes of CCTO and BaTiO 3 powders were carried at 1050°Cand 1100 °C for 4 h, respectively. The synthesized powders were mixed in acetone according to the formula (1-x)CCTO-(x)BT for 2 h and dried at 400 °C for 1 h, after that the powders were crushed in agate mortar and pressed into pellets of about 12 mm diameter and 1.5 mm thickness. Then, the pellets sintered at 1050°C for 8 h and left at room temperature. The samples surfaces were coated by silver paste to serve as poles for the electrical measurements uses. Characterization of (1-x)CaCu3Ti4O12− − − − −xBaTiO3XRD analysis: The crystal structure of (1-x)CCTO-xBT was determined by using an X-ray diffractometer with a scanning rate of 0.02°/min for 2θ range 20°-80° by employing CuKα radiation wavelength λ = 1.5406 Å (diffractometer system = XPERT-PRO) under the conditions of 40 KV and 30 mA.Raman spectroscopy analysis: A micro Raman spectrometer, equipped with an excitation source of monochromatic with wavelength of 410 nm, was used to study the relationship between Raman lines and different types of atomic motions of CCTO and BaTiO3 in the (1-x)CCTO-xBT ceramics. After the sample processing, Raman spectra was collected at room temperature.Dielectric measurements analysis: The electrical properties of the ceramics were measu...

The Ba0.95Bi0.05Ti1-xFexO3 ceramics at (x=0.0, 0.1 and 0.2) were prepared by the solid-state reaction method. The effect of iron substitution on structural and dielectric properties of Ba0.95Bi0.05TiO3 ceramic was studied. These compounds are found to crystallize in only tetragonal phase for x = 0.0 and 0.1 and the mixture of tetragonal and hexagonal phases for x = 0.2. The dielectric properties of Ba0.95Bi0.05Ti1-xFexO3 ceramics at x=0.0, 0.1 and 0.2 of Fe -doping concentration. The dielectric measurements as a function of temperature and frequency are studied and showed two diffuse phase transition and relaxation phenomena. The evolution of dielectric permittivity as a function of the frequency of undoped Ba0.95Bi0.05TiO3 show a relaxation phenomenon for which is displaced to the higher frequencies accompanied by a decrease in dielectric constant when x increase. The Complex impedance Cole-Cole plots showed a negative temperature coefficient of resistivity (NTCR) behavior of the Ba0.95Bi0.05Ti1-xFexO3 materials and increased in grain and grain boundaries resistivity. The relaxation behavior in the test materials is found to be of non-Debye type.

The effect of substitution of Baryum by Bismut in site A and titanium by iron in site A on structural, physical and electrical properties of Ba1-xBixTi0.80Fe0.20O3 ceramics at (x=0.00, 0.05, 0.10 and 0.15) was investigated by X-ray diffraction, Scaning Electron Microscopy (SEM) as well as dielectric characterizations. The crystal phase was studied by using rietveld refinement. The result of rietveld refinement of X-ray powders diffraction of Ba1-xBixTi0.80Fe0.20O3 shows that these compounds crystallize in tetragonal (P4mm) and hexagonal (P63mmc) for x=0.00 and 0.05 while at x=0.10 and 0.15 the hexagonal phase disappears and the tetragonal phase is stabilized. The structural parameters and the R-factors of these ceramics were succefully determined by the rietveld refinement. The Raman spectra confirms the disappearance of hexagonal phase in benefit of tetragonal phase as the Bi substitution increases. The dielectric measurements as function of temperature are studied and showed tree diffuse phase transitions transition from the ferroelectric rhombohedral phase to the ferroelectric orthorhombic TR-O phase and the second one is from the ferroelectric orthorhombic phase to the ferroelectric TO-T tetragonal phase. While the third one at high temperatures is the phase transition from the ferroelectric tetragonal phase to the paraelectric cubic phase Tm. These phases transition were displaced to the lower temperature with increasing of Bi substitution. And the value of dielectric permittivity increases gradually with increasing of Bi2+ contents. All these phase transitions showed a diffused phenomenon which can be well described by fitting the modified Ushino relation, 1/ε’r = 1/ε’r,max [ 1+ ((T-Tm)/2δ)γ]. The complex impedance Cole–Cole plots showed negative temperature coefficient of resistivity (NTCR) behavior of the Ba1-xBixTi0.80Fe0.20O3 for x=0.05 to 0.15 materials and decrease in grain and grain boundaries resistivity. The relaxation behavior in the test materials is found to be of Debye type.

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The dielectric properties of iron and bismuth co-substituted BaTiO3 ceramic with the formula: Ba 0.95Bi 0.05Ti 1-xFe xO3 (BBTFx) for x=0.00 to 1.00, synthesis with solid state route, were characterized. The results of dielectric permittivity dependence of temperature show three dielectric phase transitions from a rhombohedral ferroelectric to orthorhombic ferroelectric (TR-O) then to a tetragonal ferroelectric phase (at TO-T), and finally to cubic paraelectric at the Curie temperature (Tc). Calculating the relaxation parameters of ΔTrelax and the dispersion factor ΔƐ’r,max/ Ɛ’r,max, we have found that all the ceramics present a relaxation and a dispersion phenomenon. And the phase transition TO-T for x = 0.00 has the highest value of ΔTrelax while the dispersion factor has the highest value for the phase transition Tm at x = 0.60. The diffuseness parameter γ refined from Uchino law showed a diffuse phase transition for all the ceramics. While γ has a value close to 1 for TR-O at x = 0.00, which indicate a standard Curie-Weiss law. The dielectric evolution as function of frequency shows a resonance behavior for x=0.00 of Fe content while for the other ceramics we obtained a classical ferroelectric behavior.

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