Che Seman Mahmood

Al 2 O 3 -SiO 2 based LTCC tape for packaging of RF devices

This paper reports the effect of firing temperature on the physical properties of the Al2O3-SiO2 based LTCC materials for RF applications. Al2O3-SiO2 material in the form of tape was prepared using mixed oxide method. The prepared tape was than laminated and fired at different firing temperatures in the range of 840 to 960degC. The physical properties of all samples were fully characterized, such as density, crystalline phase, dielectric and thermal expansion properties. It was found that the firing temperature influences the dielectric properties of the developed tape. In this study, the sample sintered at 880degC has the best dielectric property with dielectric constant, (epsivr) of 5.65 and dielectric loss, (tan delta) of 0.003 and this is suitable for RF applications. The CTE value of this sample is 2.63, which is close to that of Si (3.0-3.5).

X-ray diffraction study of crystalline barium titanate ceramics

In this study, BaTiO3 ceramics have been prepared via solid-state reaction method. The powders were calcined for 2 hours at different temperatures ranging from 600°C to 1200°C. Using X-ray diffraction with a Rietveld analysis, the phase formation and crystal structure of the BaTiO3 powders were studied. Change in crystallite size and tetragonality as a function of calcination temperature were also discussed. It has been found that the formation of pure perovskite phase of BaTiO3 began at calcination condition of 1000 °C for 2 hours. The crystal structure of BaTiO3 formed is in the tetragonal structure. The second phases of BaCO3 and TiO2 existed with calcination temperature below 1000 °C. Purity, crystallite size and tetragonality of BaTiO3 powders were found to increase with increasing calcination temperature.

Characterization of alumina-based LTCC composite materials: Thermal and electrical properties

The study on Low temperature co-fired ceramic (LTCC) has been widely investigated due to its potential as an advanced approach for packaging of electronics devices. This paper evaluates and discusses about the firing temperatures effect on the densification, thermal and electrical properties of the prepared LTCC material. The LTCC tape, which consists mostly of Al2O3 was fabricated using tape casting technique. Five layers of tapes were then stacked and air-fired at different temperatures of 840, 880, 920 and 960°C. All samples were characterized for thermal and electrical properties. The crystallinity and microstructure of all samples were studied using XRD and SEM respectively. Current investigations show that the changing of density or volume fraction of pores is the main reason for the dielectric properties shift. Meanwhile, the changing in lattice parameters is observed as the main reason in thermal diffusivity shift. The sample fired at 880°C has the best thermal and electrical properties with thermal diffusivity of about 0.62 mm2/s, dielectric constant (εr) of about 5.65 and dielectric loss, tan (δ) of about 0.003.

Study of temperature effect on microstructures of MCIC ceramic substrate using small angle neutron scattering

Abstract The effect of firing temperature on microstructure and dielectric properties of ceramic substrate was studied. The substrate which consists mostly of Al2O3 was fabricated using tape casting technique. Three ceramic substrate samples were fired at different temperatures of 1100, 1300 and 1500°C. All samples were characterised for dielectric properties. Pore characterisation was carried out using small angle neutron scattering technique, and X-ray diffraction was used to determine grain growth. The present investigation shows that pore/grain boundary relaxation is the foremost reason of dielectric loss in this Al2O3 substrate in the low frequency region and grain size effect (interfacial grain boundary) was concluded to be less significant. This pore/boundary relaxation is found mostly originated from intragranular pore.

Structural and morphological properties of PbTiO3: The effect of SiO2 as an additive

Ferroelectric materials have found many applications in a wide range of capacitors, transducers, sensors, light valves and motors. Their properties are related to the routes they are processed. Ferroelectric materials in their bulk polycrystalline form are difficult to fabricate in shapes and sizes suitable for device applications. This is due to cracking occurs during sintering process. This has lead to research being undertaken to produce a crack free dense polycrystalline ferroelectric samples by using additives. Therefore in this study PbTiO2 powders with addition of SiO2 as an additive were synthesized by solid-state reactions using different SiO2:PbTiO3 weight ratios (0.1:0.9, 0.05:0.95 and 0.03:0.97). Structural and morphological changes were studied using XRD and SEM with regard to after the addition of SiO2 at sintering temperatures 900 °C, 1000 °C and 1100 °C.

Effect of Impact Milling and Ball Milling on Microstructure of Lead Titanate Powders Synthesized by Solid-State Reaction

Single phase lead titanate (PbTiO3) was prepared by solid-state route using lead (II) oxide (PbO) and titanium dioxide (TiO2) as precursors. The effects of using impact mill (IM) and ball mill (BM) in solid state reaction have been observed. X-ray diffraction (XRD) pattern was recorded at room temperature and analyzed by employing Rietveld method. X-ray diffraction (XRD) pattern shows that the PbTiO3 particles are tetragonal with tetragonality (c/a) ratio ranging from 1.058 to 1.063 and average crystallite size from 40.8 to 64.2 nm. It is found that the impact mill (IM) can be used to produce pure tetragonal perovskite with a lower tetragonality and average crystallite size.

Electrical and Magnetic Studies of (La0.5-xPrxBa0.5)(Mn0.5Ti0.5)O3 as Multiferroic Material

A new perovskite based titano-manganite (La0.5-xPrxBa0.5)(Mn0.5Ti0.5)O3 at x concentration 0, 0.01, 0.03, 0.05, 0.07 and 0.09 has been successfully prepared by ceramic solid-state technique at sintering temperature of 1300 °C. Dielectric electrical properties of the synthesized materials at frequency ranging from 5 Hz to 1 MHz and magnetic properties have been studied at room temperature. Analyses have been carried out to determine the structural, magnetic and dielectric properties of the synthesized material as a candidate of multiferroic material.

The Effects of Sintering Temperature Variations on some Physical Properties of Al2O3-SiO2-PbO-MgO Laminated Tape System

An Al2O3-SiO2-PbO-MgO laminated tape system was prepared to investigate the dependence of some physical properties on various sintering temperatures, 840 °C, 880 °C, 920 °C and 960 °C. The results show that the effect of the increasing sintering temperatures was a fluctuating in the density value of the laminates. It was also observed that the dielectric constant and dielectric loss showed the lowest value for the sintering temperature of 880 °C. SEM micrographs of the laminate samples shows a mixture of grain sizes and the samples had a combination of small and large pores with the average grain size around 2.20-2.64 m.