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The ion irradiation-induced phase transformation in a AlCuCoGe decagonal quasicrystal has been studied by means of in situ transmission electron microscopy. Prior to ion irradiation, typical single decagonal quasicrystalline HRTEM images and electron diffraction patterns along the tenfold axis were observed. The HRTEM image clearly showed the decagonal quasicrystal structure and revealed no apparent defects in the unirradiated material. After a 1.5 MeV Xe+ ion irradiation to a dose of 4.3 × 1014 ions/cm2, electron diffraction and HRTEM images indicated that the original, single quasicrystal had transformed into amorphous and bcc crystalline components. Moreover, the amorphous component had the same composition as the original quasicrystal, and the bcc crystalline component lacked aluminum as compared with the quasicrystal. The crystalline component was much more resistant to amorphization than the quasicrystalline structure. The phase transformation and separation observed in the Xe+ ion irradiated AlCuCoGe quasicrystal were due to irradiation-induced defect accumulation and compositional segregation. During the annealing of the Xe+ ion-irradiated specimen, the electron diffraction pattern of the crystalline phase component did not change with the increasing temperature. However, a transition from amorphous-to-quasicrystal was observed during annealing at different temperatures.

Structure changes of an α-AlMnSi phase, irradiated with 1.5 MeV Xe+ ions at room temperature, have been studied by transmission electron microscopy (TEM). At an irradiation dose of 3.4 × 1013 ions/cm2, the primitive cubic α-AlMnSi phase transformed to a bcc phase. But the unit cell parameter (a = 1.268 nm) remained the same. With an increase of irradiation dose, the bcc phase became amorphous at 3.4 × 1014 ions/cm2. The bcc phase structure consists of two MacKay icosahedral atomic clusters in each unit cell. A pseudo ten-fold rotational axis has also been obtained via electron diffraction in the specimens irradiated to 5.1 × 1013 ions/cm2. This quasicrystal-like structure was found for the first time during the radiation-induced crystalline-to-amorphous phase transformation. Annealing of the fully amorphized specimens was performed with in situ TEM. The α-AlMnSi phase started to form at 350°C and was fully crystallized at 500°C. The bcc phase and quasicrystal-like structures were not observed during the crystallization processes.

A rapidly solidified aluminium alloy of nominal composition 7.5 wt.% Cu and 2.5 wt.% Fe was investigated by transmission electron microscopy. The material was seen to have a fine, homogeneous cell structure with a high dislocation density within the cells. Interconnected particles of the iron-rich AlFeCu-type quasi-crystalline (QC) phase were found to exist on cell boundaries, coexisting with a low fraction of the tetragonal body-centered θ-Al2Cu phase. Indications are found that the QC particles are connected through 3-fold axes. The QC is found to accomodate nearly all Fe in the alloy. An in situ heat treatment at 300 °C caused precipitation and growth of the θ-Al2Cu phase. The Cu contents in matrix and in the QC phase were seen to decrease. No transformation or growth of the QC phase could be observed. No other phase except for the QC phase was found to contain iron in the alloy. Weak orientation relationships between the QC phase and the θ phase and between the two phases and the aluminium matrix have been found.

Microstructures in intergrown 123 and CuO material prepared by solid state reaction have been examined by transmission electron microscopy (TEM). Samples are of nominal composition Y:Ba:Cu=1:2:4. As produced, samples are often found to exhibit microstructure with disordered cations which leads to a distortion of the (001) planes in the 123 structure. After annealing (780°C, 1 atm. O2 for 30 days), it is found that the equiaxial CuO particles can be partially dissolved, forming a structure with intercalations of excess CuO layers in the 123 grains on the (001) plane. This interaction can be ordered over short distances. In the intergrown 123 and 124 phases, 3-6-11, 4-8-15, 3-6-10 and 5-10-16 structures with c=38.8, 104.9, 73.9 and 120.6 A , respectively, have been found to exist in this material. These results indicate that the post-annealing process influences the microstructure of the intergrown materials and that new long-period phases can be made in the Y-Ba-Cu-O system.

Increased current density per bump is inevitable with the growing demand for miniaturization. Hence, the electromigration failure mode of bumps is critical to determine the bump current carrying capability. This paper presents the electromigration failure study of the copper pillar (Cu-pillar) bump and compared to that of the solder bumps. Our analysis shows that the Cu-pillar bump could handle higher current which is attributed to its unique structure. Conducted experiment shows that the electromigration failure location of the pillar-bump is away from the high current crowding point where the solder bump failure is. Cu-pillar bump electromigration failure is attributed to the depletion of intermetallic compound (IMC) at the Cu pillar's Cu-Sn interface, which was studied to have a longer failure time than dissolution of under bump metallization (UBM) in most solder bumps (Jang, 2002). In addition, Cu-pillar's excellent thermal dissipation characteristic could facilitate devices to operate at a lower temperature when compared to devices utilizing inferior thermal characteristic bumps. Because reduced temperature slows the electromigration failure, device packaged with Cu-pillar would be more competitive as compared to device which uses solder bumps. With various factors pointing towards a better electromigration performance, Cu-pillar bumps could easily achieve an order improvement in terms of mean-time-to-failure with respect to traditional bumps

In an earlier paper we have reported about prelimary results of evaporated CoNi/Pt multilayers [1] The main result at that time was a substantially lower Curie temperature for a Co60Ni40/Pt multilayer in comparison with the known Co/Pt having the same magnetic parameters. A study of the bulk magnetic phase diagrams shows a lowered Tc for adding Ni into Co. The problem by tailoring the composition for the Tc is that one also have to consider the Kerr rotation because this value scales with the magnetic moment of the multilayer.

Experimental and calculated results based on the finite-difference time-domain method are presented on the impedance and radiation characteristics of the classic shorted quarterwave patch. It is found that, for foam substrates with relative permittivity close to unity, the bandwidths of the quarterwave patches are significantly larger than the halfwave patches. On the other hand, for microwave substrates with relative permittivites equal to 2.32 and 4.0, the bandwidths of quarterwave patches are less than those of halfwave patches, owing to the excitation of surface waves. The maximum gain in the case of foam substrate is in the range of 2–3.5 dBi, occurring 0–45° from broadside, depending on the substrate thickness. The use of a partial short, while reducing the resonant frequency, also decreases the bandwidth. The paper also describes the application of the shorting-wall principle to realise a compact wideband L–probe patch antenna.

The icosahedral quasicrystalline (IQ) phases of rapidly solidified materials, and especially that of the AlMnSi type, have been subjected to intensive research in recent years. These phases have been found to be closely related to periodic phases of similar composition, and orientation relationships have been found between the IQ and its decomposition products. Consequently, they are also of great importance in the study of the IQs. The most recognized periodic phase in this respect is probably the primitive α-AlMnSi phase (a = 12.68 Å). The 138 atoms in the unit cell are arranged in large atomic clusters, the socalled Mackay Icosahedra, with slightly deformed icosahedral symmetry. These clusters are believed also to be the building blocks of the quasicrystals and of some additional periodic decomposition phases, the difference between the structures being realized through a different stacking of the clusters. A thorough understanding of these periodic phases is therefore clearly important. Here we present a study of some of the defects that frequently appear in the α-phase.

Since the icosahedral quasicrystal (IQ) was first reported and described, transmission electron microscopy (TEM) has played an important role in structural studies of the material. Several types of IQ structural models have been reported, but the detailed structure is still not solved. In addition the quasicrystals are frequently strained and dislocation models have been suggested. The present investigation is focused on these latter aspects through TEM-studies of interface boundaries and defects in a rapidly solidified Al-Mn-Cr-Si alloy.The bright field image in Fig. 1 shows IQ precipitates in an Al-matrix. The particles have two different orientation relationships with the matrix. These relationships have been found through detailed determination of the reciprocal lattice for several particle/matrix combinations. The diffraction pattern in Fig. 2a shows a Al zone. Here three orthogonal 2-fold axes in the quasicrystal are along the three 4-fold aluminium axes. In Fig. 2b one of the three orthogonal 2- fold axes is along a cube direction and the two others along two orthogonal axes in the facecentered Al matrix. The first relationship corresponds to the one observed previously for much smaller icosahedral particles.

JIAOTONG UNIV,DEPT MAT SCI & ENGN,SHANGHAI,PEOPLES R CHINA. DALIAN INST TECHNOL,DEPT MAT ENGN,DALIAN,PEOPLES R CHINA.;KUO, KH (reprint author), ACAD SINICA,INST MET RES,ATOM IMAGING SOLIDS LAB,SHENYANG,PEOPLES R CHINA

Zircon, ZrSiO4, is a prospective durable host material for the immobilization of excess weapons plutonium. Using cerium as a chemical analogue for plutonium, the experiments on the synthesis of Ce-doped zircon were conducted by sintering of sol-gel precursors in air and vacuum. The results showed that cerium substantially promotes zircon formation from sol-gel precursors and sintering in air is preferable for cerium incorporation in zircon structure. Based on measured lattice constants, solid solution compositions (Zr0.96Ce0.04)SiO4 and (Zr0.98Ce0.02)SiO4 were formed in samples sintered in air at 1400°C and 1600°C, respectively. The solubility limits of cerium and actinides in zircon and mechanism of zircon formation are discussed.