Icosahedral boron phosphide (B12P2) was directly synthesized from elemental powders by a high-temperature reaction under an argon pressure. Powder diffraction data were collected for two B12P2 samples, and diffraction patterns were compared with calculated patterns of phosphorus deficient crystals: B12+xP2−x for 0<;x<0.2. The as-synthesized B12P2 appears to be close to its ideal stoichiometry based on the consistency between the observed and the calculated values of the relative intensity for all diffraction planes below 90° 2θ.

The silicon-rich end of the Si-B phase diagram, defining the silicon boride(s) that coexist in equilibrium with boron-saturated silicon, is poorly known. Understanding this equilibrium has implications for the processing of p+ silicon wafers, whose boron concentrations are near the solubility limit. Additionally, silicon boride precipitates produced by boron-ion-implantation and annealing of crystalline silicon have recently been shown to be efficient internal getters of transition metal ions. The experiments described in this paper probe the stability of these silicon borides. A phase with a boron-carbide-like structure, SiB3, grows from boron-saturated silicon in both the solid and the liquid state. However, SiB3 is not found to be stable in either circumstance. Rather, SiB3 is a metastable phase whose formation is driven by the relative ease of its nucleation and growth. The silicon boride that exists in stable equilibrium with boron-saturated silicon is SiB6. A qualitative understanding of the metastability of SiB3 comes from recognizing the conflict between the bonding requirements of icosahedral borides such as SiB3 and the size mismatch between silicon and boron atoms.

We review the synthesis methods and properties of single crystal, powder, and thin film TlBaCaCuO high-temperature superconducting (Tl-HTS) materials. With transition temperatures ≥ 100 K for several compounds, Tl-HTS materials present real opportunities for applications above 77 K. Experiments using (1) single crystals: determined precise structural parameters and identified the complex Tl1+–Tl3+ equilibrium model; (2) powders: studied the complex thermodynamic phase diagram; and (3) epitaxial films: studied fundamental properties such as electron pair symmetry and the effect of controlled extrinsic defects on flux pinning strength, as well as providing the large-area surfaces required for device applications.

Future Si microelectronic devices will require increasingly stringent limits on transition-metal impurities. There is thus a need to develop new methods for impurity gettering that rely on gettering sites that are active for arbitrarily small impurity concentrations, below the characteristic solid solubility at which metal suicides precipitate. These sites must also be highly preferred relative to solution sites in the Si matrix even at elevated temperatures. One such method has been developed that is also expected to be compatible with front (device) side gettering enabling smaller diffusion lengths for lower processing temperatures. This method involves boron implantion in the front side to levels above the boron-saturation limit and annealing to generate the gettering sites. The gettering layer is introduced at a depth beneath the device zone through appropriate choice of implantation energy. SIMS compositional profiling shows transition metals are strongly gettered within the boron-supersaturated layer. The purpose of this study was to identify the structure and composition of the gettering sites within the boron-supersaturated layer.

The thermodynamic stability of TlBa2Ca2Cu3O9–y (1223) and substitutionally related phases has been studied by performing extended high-temperature anneals in a two-zone furnace. This approach allows for independent control of each of the thermodynamic variables: the oxygen and thallous oxide partial pressures [P(O2) and P(Tl2O)], the sample temperature, and the sample composition. P(Tl2O) determines which of several superconducting phases form in the unsubstituted Tl–Ba–Ca–Cu–O system. TlBa2Ca2Cu3O9–y is stable only within a narrow window of P(Tl2O). Partially replacing Tl with Pb and Ba with Sr substantially increases the stability of the 1223 phase. The composition (TlxPb0.5) (Sr1.6Ba0.4)Ca2Cu3O9–y yields only the 1223 phase under two-zone conditions when P(Tl2O) exceeds a lower bound. The stability of Pb- and Sr-substituted 1223 relative to the 1212 phase is related to the substitutional stoichiometry, rather than P(Tl2O).

Boron carbides are refractory solids with potential for application as very high temperature p-type thermoelectrics in power conversion applications. The thermoelectric properties of boron carbides are unconventional. In particular, the electrical conductivity is consistent with the thermally activated hopping of a high density (≈ 1021/cm3) of bipolarons; the Seebeck coefficient is anomalously large and increases with increasing temperature; and the thermal conductivity is surprisingly low. In this paper, these unusual properties and their relationship to the unusual structure and bonding present in boron carbides are reviewed. Finally, the potential for utilization of boron carbides at very high temperatures (up to 2200°C) and for preparing n-type materials is discussed.

We compare electron spin resonance (ESR) spectra of B4C samples made by three methods. The samples are 1) two ceramics made by hot-pressing boron and carbon powders, 2) a polycrystal made by carbothermic reduction, and 3) a single crystal grown from a palladium metal melt. All samples show remarkably similar spectra between 2 and 100 K. In particular, all samples show a single Lorentzian absorption, a linewidth that decreases with increasing temperature, and an inverse temperature dependence of the integrated intensity. The integrated intensity of the paramagnetic spin signal corresponds to a density of 2×1019/cm2 localized spins. Having a single crystal sample enables us to meaningfully measure the angular dependence of the ESR linewidth. This angular dependence is consistent with the paramagetic centers being unpaired electrons centered on the central carbon atoms of positively charged C-C-C intericosahedral chains. These chains appear to replace 0.5 % of the positively charged C-B-C intericosahedral chains which occur in B4C.

Boron carbides exhibit an anomalously large Seebeck coefficient with a temperature coefficient that is characteristic of polaronic hopping between inequivalent sites. The inequivalence in the sites is associated with disorder in the solid. The temperature dependence of the Seebeck coefficient for materials prepared by different techniques provides insight into the nature of the disorder.

The crystal structures of several icosahedral boron-containing compounds have been refined using MoKα intensity data. Preparation of crystals differs from previous procedures, with boron carbide grown from molten copper and boron arsenide by arsenic vapor transport. The structures consist of icosahedral units bonded together with direct B-B bonds as well as other linkage units (B-C-B and As-As chains).

The recent discovery of superconducting oxide ceramics with critical temperatures (Tc) near 100°K has stimulated research at an unprecedented pace. Single phase YBa2 Cu30x (x = 6.9), the subject of most of the interest, is an oxygen deficient 1:1:3 stacked perovskite derivative, (The structure of this materials has been described by a number of authors, many of whom are referenced by Jorgensen et al.) At room temperture it has an orthorhombic structure with lattice parameters near: a = 3.82Å, b = 3.88Å, and c - 11.68 Å. At lower oxygen values (x≤6.5) the structure is tetragonal with lattice parameters near: a = 3.86 and c = 11.80. It has been suggested that tetragonal YBa2 Cu30x is not superconducting. YBa2 Cu30x, regardless of oxygen content, is referred to here as 123.

Boron-rich refractory solids based on the rhombohedral structure of α-B exhibit electrical properties that range from a hopping-type semiconductor (boron carbide) to wide bandgap room temperature insulators (the boron pnictides B6P and B6As). As such, they are of interest for a variety of high temperature semiconductor applications. Preparation techniques for these unusual materials are reviewed, and new results on the crystal growth of boron carbides and B6As and on thin film deposition of B6P are presented.