Mohd Sobri Idris

Structure Refinement Strategy of Li-Based Complex Oxides Using GSAS-EXPGUI Software Package

This paper discussed refinement strategy that been used to reveal crystallographic properties of lithium-based complex oxides with layered rock salt structure. Rietveld analysis using XRD data was used to determine the amount of interlayer mixing and estimate oxygen contents. The structural model and refinement methodology was controlled and validated initially using a standard sample. Thus, this paper summarized structure refinement strategy that been used to quantify the degree of cation order associated with interlayer mixing and investigate the sensitivity of laboratory XRD data to oxygen non-stoichiometry that recently published elsewhere [.

Electrical Properties of Fresnoite Ba2TiSi2O8 Using Impedance Spectroscopy

Fresnoite with composition Ba2TiSi2O8 (B2TS2) was first found in 1965, adopting a non-centrosymmetric structure. It also reported to crystallize in a tetragonal unit cell with a=8.52Å and c=5.210Å leading to some possible application as hydrophone, transducer and second harmonic generation and low temperature co-fired ceramics (LTCC). B2TS2 were synthesized by conventional solid state reaction. Phase pure B2TS2 was obtained after heating the pellets at a final sintering temperature of 1230 °C in air at 92 h. Study found that Fresnoite B2TS2 is a type of materials which are not ferroelectric and instead show perfect dielectric insulator behaviour with resistance >106Ωcm at temperatures below 750°C and also shows nonideal debye respone. The activation energy for conduction of B2TS2 samples is very high, indicating that these materials are highly insulating.

Review on dielectric properties of rare earth doped barium titanate

Rare earth doped Barium Titanate (BaTiO3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO3 downshifted the Curie temperature (TC). Transition temperature also known as Curie temperature, TC where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO3, Er-doped BaTiO3, Sm-doped BaTiO3, Nd-doped BaTiO3 and Ce-doped BaTiO3 had been proved to increase and the transition temperature or also known as TC also lowered down to room temperature as for all the RE doped BaTiO3 except for Er-doped BaTiO3.

Trends of microwave dielectric materials for antenna application

Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (er), high quality factor (Q f ≥ 5000GH z) and good temperature coefficient of resonant frequency (τf). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

Structure refinement of Ba0.5Sr0.5Co0.8Fe0.2O3-d as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

Ba0.5Sr0.5Co0.8Fe0.2O3-δ was successfully prepared using modified solid-state synthesis routes. The lowest temperature to obtained single phase of Ba0.5Sr0.5Co0.8Fe0.2O3-δ is about 900°C for 15 hours. Longer period of time are required compared to only 5 hours at 950°C as established in literatures. The X-ray Diffraction (XRD) data confirmed that Ba0.5Sr0.5Co0.8Fe0.2O3-δ is formed a cubic perovskite with the space group of Pm-3m. The lattice parameters of Ba0.5Sr0.5Co0.8Fe0.2O3-δ are a = 3.990 (1) A and unit cell volume is V = 63.5 (1) A3. The Rietveld refinement of XRD data revealed that the crystal structure of Ba0.5Sr0.5Co0.8Fe0.2O3-δ slightly changes as a function of temperature.

The Existing of Oxygen Nonstoichiometry in Complex Lithium Oxides

The possibility of oxygen deficiency in lithium-based complex oxides particularly for layered rock salt structures has little attention in the literature, in spite of the importance of these materials as potential lithium battery cathodes. This paper briefly reviewed the existing of oxygen non-stoichiometry in complex lithium oxides and their effect to perfomance of cathodes in lithium ion batteries.

Determination of Interlayer Mixing and Oxygen Non-Stoichiometry in LiNi0.8Mn0.1Co0.1O2-δ Using Powder Diffraction Data

The effect of preparation conditions, temperature and atmosphere, on oxygen stoichiometry and interlayer cation mixing in the layered rock salt material LiNi0.8Mn0.1Co0.1O2-δ has been investigated using X-Ray powder diffraction, including Rietveld refinement. Interlayer mixing occurs as a direct consequence of oxygen deficiency; samples with least oxygen deficiency and most cation order were obtained on firing in O2 at ~ 900 950C.

X-Ray Diffraction and Dielectric Constant of Lanthanum Doped Barium Titanate Ceramics

Undoped barium titanate and lanthanum (La) doped barium titanate (BaTiO3) were studied for ferroelectric properties with the formula of Ba1-xLaxTi1-x/4O3 for x=0.1 and being prepared by using conventional solid state method reaction. The pure phase of this composition which x=0 were found at final heating temperatures starting from 1300°C and x=0.1 at 1350°C for overnight in air with intermittent grinding. The changes in the crystal structure of the composition were detected by using X-ray diffraction. Impedance Spectroscopy analysis is carried out to determine the dielectric properties for undoped BaTiO3 and La doped BaTiO3 for x=0.1.

Structural Analysis of LiNi0.7Mn0.3O2 as Cathode Material for Rechargeable Lithium-Ion Batteries

The layered rock salt LiNi0.7Mn0.3O2 was prepared by conventional solid-state synthesis route. The prepared samples were analysed using X-ray diffraction (XRD) to determine purity of samples. Then, structural analysis and crystallographic properties of samples were analysed using Rietveld refinement. Rietveld refinement results indicated that the amount of cation disorder in the layered rock salt structure highly influenced by temperature and synthesis conditions. The most optimum temperature to obtain the highest degree of cation ordering is between 850oC and 900oC in air.

Microwave and Electrical Properties of Zr-Doped SrTiO3 for Dielectric Resonator Antenna Application

Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from SrTi1-xZrxO3 ceramic with different substitution of Zr in place of Ti for (0 ≤ x ≤1). Ceramic powder were prepared using conventional solid state reaction method. X-ray Diffraction exposes physical properties Zr-doped SrTiO3 which exhibit phase transition from cubic, tetragonal to orthorhombic phase. The electrical properties such as dielectric constant (εr) and dielectric loss (tan δ) were studied in variation of temperatures and frequencies. At room temperature the dielectric constant decreased from 240 to 21 with increase of Zr content however the amazing result was obtained for multiband antenna by Zr content. The dielectric loss obtain shows very low loss value roughly below 0.07 for all samples. The variations of return loss, resonance frequency and bandwidth of CDRAs at their respective resonant frequencies are studied experimentally.