Abstract: The Ni1-xCuxO was prepared from raw materials of NiO and CuO via solid state reaction. This study was focuses on undoped and CuO doped NiO properties. CuO was used as dopant with five different concentrations. The powders were mix for 24 hours and followed by calcinations at 900°C for 2 hours. The calcined powders were compacted to a 5 mm diameter pellet form, by applying 200 MPa pressure. Then, the pellets were sintered at temperature 1200°C for 12 hours. After that, the samples were analyzed by using XRay diffraction (XRD) in order to identify the phase formation, scanning electron microscopy (SEM) for the microstructure and surface topography observation, density measurement by Archimedes principle and impedance analyzer in order to measure the dielectric properties. XRD results show that all sintered pellets produce a single phase of Ni1-xCuxO. In addition, increase of Cu dopant concentration causes the lattice parameter getting larger. Apart from that, SEM shows that more addition of Cu dopant increase the grain size. The density is also improved, due to formation of bigger grain size lead to an increasing in density. Impedance analyzer results show the dielectric behaviour of the samples was improved with increasing of CuO content. The 0.10 mol% CuO obtained optimum dielectric properties with lowest dielectric loss measured at 1 GHz (0.008).
Abstract: Porous Sb-doped barium titanate (Sb-BaTiO3) ceramics were fabricated by adding various amounts of graphite powders. The density, structure, microstructure, porosity and electrical resistivity of the porous Sb-BaTiO3 ceramics produced without and with graphite were investigated. All the sintered ceramics showed a tetragonal perovskite structure, irrespective of the amount of graphite added. The porosity of the ceramics increased and the grain size decreased with increasing graphite addition which mainly due to the exothermic reactions of the graphite and oxygen molecules in the ceramics. The prepared porous Sb-BaTiO3 ceramics exhibit PTCR behavior where the PTCR jump of the ceramics with graphite was about 103 which is higher than that of the ceramics without graphite. The increasing in the PTCR jump with increasing graphite addition was attributed mainly due to the increase in the electrical barrier height of grain boundaries and the porosity. It was found that the graphite is an effective pore forming agent for fabricating porous BaTiO3-based ceramics.
Abstract: Barium titanate with 10% barium ferrite substitution (BaTiO3-BaFe12O19) has been synthesized by the solid state reaction route. Formation of the BaFe12O19 phase confirmed its existence in the composite. Impedance spectroscopy study of the composite sample was performed at different temperatures of 25, 40, 80, 120 and 160 °C. BaFe12O19 substituted sample shows a single semicircle at lower temperature and two overlapped arcs at 120 and 160 °C due to grain and grain boundary. The impedance plots were fitted based on a parallel R-CPE circuit. The grain boundary resistance behaves like the positive temperature coefficient of resistivity (PTCR) for donor-doped BaTiO3 semiconductor. The highest capacitance is contributed by the grain boundary at 80 °C.
Abstract: In the ZnO based varistor, the improvement of nonlinear coefficient (α) and prevention of evaporation of Bi2O3 during heat treatments can be achieved by the addition of MnO2 or Co3O4. In this conjunction, it is proper to see the effect of these additives at different low mol percentage and sintering conditions to nonlinear coefficient improvement of the varistor ceramics. In this paper, the investigation regarding to the α variation of Co3O4 doping on ZnO-Bi2O3-TiO2 system is discussed. Here, the crystalline phases were identified by an XRD (PANalytical (Philips) XPert Pro PW3040/60) with CuKα radiation and the data were analyzed by using XPert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size (d) was determined by lineal intercept method. The α of ZnO doped with 0.5 mol% of Bi2O3, 0.5 mol% of TiO2 and x mol% of Co3O4 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of α is done by using Origin Pro8.0 software. The value of α at low concentration at 1170 °C has the value 5.36 and 3 at 45 and 90 min sintering time, respectively, and then decreases to 4.99 and 2.98 at 0.8 mol% Co3O4 concentrations. When the amount of dopant is increased then the value of α increase up to 0.4 mol% and then the value are slightly dropped after further addition. The addition of Co3O4 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of α to increase up to 0.4 mol% and decrease after further addition.
Abstract: Pt-SnO2 ceramics were prepared via solid-state route from a mixture of powders of (100-x) SnO2.x Pt (0≤ x wt %≤ 1). The samples were then sintered at 600, 800 and 1000 °C for 3 hours. The resulting samples were then characterized using Laser Flash Apparatus (LFA) for determining thermal diffusivity (α ) value. The measurements of α were carried out at room temperature up to 400 °C with the intervals of 50 °C. Experimental results showed that thermal diffusivity value is in the range of 5.0×10-7m2s-1 - 3.0×10-6m2s-1. We also show that larger grain size increases the thermal diffusivity of the ceramic. Data concerning the effects of additive amount, pore content, and temperature were also reported.
Abstract: Tuning the physical properties of inorganic glass-ceramics through controlled doping of magnetic nanoparticles is topically challenging. A series of glass-ceramic having chemical composition 75P2O5-17MgO-(3-x)TiO2-5Li2O with x = 0 to 3 mol% containing nickel oxide (NiO) nanoparticles (NPs) are prepared by melt quenching method (MQT) via heat treatment at 350 °C. The effect of NiO NPs on thermal and magnetization response are examined. X-Ray Diffraction (XRD) pattern confirm the amorphous nature of the samples. Differential Thermal Analysis (DTA) measurement shows the decrement of glass stability from 327°C to 295°C with the increase of titanium dioxide (TiO2) contents which are glass seem to be unstable. Significant increase in the magnetization is evidenced with the increase of NiO nanoparticles from 1.5 mol% to 2 mol%. The improved physical properties of these glass-ceramics suggest their usefulness in photo-electronic.
Abstract: The CaTiO3 samples were prepared by high-energy ball milling process followed by sintering process from 1040 to 1200°C. X-ray diffraction (XRD), microstructural analysis, and dielectric properties over a wide range of frequency varying from 0.01 Hz to 1 GHz at room temperature were investigated. The formation of a single phase CaTiO3 with orthorhombic structure was achieved at 1120°C and above. From a morphological point of view, sintering temperature promoted grain growth. Dielectric properties in the frequency range 0.01 Hz - 1 MHz revealed a relaxation-type process. Interfacial phenomena were the possible physical mechanisms that gave rise to these relaxation-type plots. Extending the frequencies above ~1 MHz yielded a frequency-independent characteristic of dielectric constant (ε'). These turned out to the relatively small dielectric loss (tan δ) values. The origin of the dielectric responses in the frequency range 1 MHz - 1 GHz was attributed to the domination of dipolar polarization. The grain size effect in sintered CaTiO3 samples was prominent, notably in dielectric responses above ~1 MHz. Increase in sintering temperature remarkably led to an enhancement in dielectric constant values and reduction in dielectric loss values. Therefore, a significant correlation existed between microstructural features and dielectric properties.
Abstract: Ceramic sample of La0.70Ba0.30Mn0.40Ti0.60O3 oxide has been prepared by the conventional solid-state reaction method. The sintered sample was characterized by using x-ray diffraction (XRD) and low frequency LCR meter. XRD result shows that the sample has a cubic structure with the existence of impurity phase. The dielectric properties of La0.70Ba0.30Mn0.40Ti0.60O3 measured from room temperature to 200°C shows that the dielectric permittivity is temperature dependence with strong dispersion at low frequencies. A circuit model based on the universal capacitor response function is also being used to represent the dielectric properties of the sample.
Abstract: Lately, researchers have been considering the miscellaneous in the borophosphate crystalline’s luminescence as one of the important properties in hunt of the new functional material. In this study we discus the structural and luminescence properties of Eu3+/Dy3+ co-doped borophosphate ceramic. A series of ceramic samples based on B2O3-(65-)P2O5-25MgO-10TeO2 where (065) mol has successfully been prepared using solid state reaction method and sintered at 900°C. The crystalline phase of the powder samples was characterized using X-ray diffraction pattern. The diffraction patterns analysis indicated that the prepared samples were polycrystalline phase of B(PO4), Mg(PO3)2and Mg(BO3)(PO4). The local structure network structure has been investigated using Infrared Spectroscopy using KBr method. The FT-Infrared spectra reveal the presence of B-O-B vibrations, BO3 and BO4 bridging oxygen and P-O stretching modes of P-O-P, P=O and PO4 unit in the ceramics sample. Meanwhile, the luminescence properties of doped sample were measured based on analysis of emission spectra of photoluminescence spectroscopy. The emission peaks of Eu3+ doped sample were located at 593 nm, 613 nm, 652 nm, 685 nm due to the assigned transition 5D0-7FJ ( J = 1, 2, 3, 4 ). The Dy3+ emission is due to 4F9/2 -5H15/2 and 4F9/2-6H13/2 transition. For Eu3+/Dy3+ co-doped sample consists of peaks belonging to the 4F9/2-6H15/2 (482 nm) and 4F9/2-6H13/2 (573 nm) transition while red emission 5D0-7F2 transitions appears at 611 nm. Improvement in the optical properties due to co-doping may be useful to discover a new highly efficient luminescent material that are very useful in optical devices and solid-state lighting.