Papers by Author: M.A. Matin

Abstract: Barium titanate (BaTiO₃) with its perovskite structure is a promising dielectric material for many applications such as transducers, actuators, high-k dielectrics and multilayer ceramic capacitors (MLCC). In this study, we have investigated the effect of sintering time on dielectric properties of BaTiO₃ and Nb-doped BaTiO₃. BaTiO₃ was doped with 0.3 mol % niobium oxide (Nb₂O₅). At first, nanosized pure BaTiO₃ and Nb₂O₅ doped BaTiO₃ were milled, dried and pressed into pellets to prepare green samples. Then, the samples were sintered at 1275°C for different time periods ranging from 2 to 5 hrs. Single stage sintering was adopted for the densification of prepared samples. Microstructure of the sintered samples was investigated employing Field-emission scanning electron microscope (FESEM). Dielectric properties of the samples were measured using an impedance analyzer. Finally, a correlation was established between the dielectric properties of the sintered samples and their microstructure. Nb has shown to provide strong inhibiting effect after sintering the samples in the range of 2 to 5 hours at 1275°C thereby, resulted in higher dielectric properties of doped BaTiO₃ ceramics compared to that of pure BaTiO₃. The best room temperature dielectric constant of 7200 was obtained for Nb doped BaTiO₃ sintered at 1275°C for five hours. Such improved dielectric constant is attributed to the optimum grain size of about 1 micron at this sintering temperature.

Abstract: This paper reports on fabricated hard magnetic cobalt nickel phosphorous (CoNiP) films with electro-chemically deposition technique on copper substrate in the presence of different urea (0 to 10 g/L) and NaH₂PO₂ (16 to 21 g/L) concentrations. Thin films were obtained at current density ranges from 5 to 20 mA/cm² and temperature varies from ambient temperature to 60°C. Magnetic properties namely coercivity, remanent magnetization, saturation magnetization and squareness of the films were studied using Vibrating Sample Magnetometer (VSM). The result showed that for bath containing higher concentration of urea (10 g/L), bright films with higher coercivity were obtained at moderate current density (15 mA/cm²) and at higher temperatures (40-60°C). In contrary, uniform and bright films were produced at ambient temperature in bath containing no urea or lower concentration of urea. Scanning Electron Microscopy (SEM) revealed that porosity and cracking tendency are increased with increasing temperature. CoNiP thin films with improved magnetic properties are thus obtained for plausible applications in high density recording media and MEMS.

Abstract: The past years have triggered considerable scientific efforts towards the predictive analysis of the reliability of solder connections in micro-electronics. Undoubtedly, the replacement of the classical Sn-Pb solder alloy by a lead-free alternative constitutes the main motivation for this. This paper concentrates on the theoretical, computational and experimental multi-scale analysis of the microstructure evolution and degradation of the conventional solder material Sn-Pb and its most promising lead-free alternative, a Sn-Ag-Cu (SAC) alloy. Special attention is given to the thermal anisotropy of bulk SAC and the interfacial fatigue failure of SAC interconnects.