Mary C. Lavine

Crystallographic Polarity in the II‐VI Compounds

Crystallographic polarity associated with the zinc‐blende and the wurtzite structures has been studied in the following II‐VI sulfides, selenides and tellurides; ZnS, ZnTe, CdS, CdSe, CdTe, HgSe, and HgTe. The CdS and CdSe have the wurtzite structure and the others the zinc‐blende structure. Consistent with theoretical calculations, the geometric structure factor for x‐ray scattering was found different in opposite directions along the polar axis. Consequently, the two types of surfaces perpendicular to the polar axis were identified. The etching behavior of these surfaces was correlated with the x‐ray results so that simple etching tests were developed for the identification of the {111} (zinc blende) or the {00.1} (wurtzite) surfaces.

The P‐T Phase Diagram of InSb at High Temperatures and Pressures

The pressure‐temperature phase diagram of InSb is refined to show the boundaries between the high‐pressure tetragonal (InSb II) and orthorhombic (InSb IV) phases and extended to about 125 kbar to locate the boundary of the new phase (InSb III). The existence of these structures as stable phases in their phase fields is demonstrated by high‐pressure, high‐temperature x‐ray studies and by x‐ray studies and superconductivity measurements on these phases retained by quenching to 77°K. The structures of InSb II and InSb IV are confirmed, and a hexagonal structure for InSb III is proposed. The hexagonal cell has the dimensions (at ∼90 kbar) of a=6.10 A and c=5.71 A with a calculated density of 8.5 g/cc. Values are reported for the compressibility of phases InSb I, InSb III, and InSb IV and for the thermal expansion coefficients, under pressure, of phases InSb I and InSb IV.

High pressure phase transition in mercury selenide

Abstract It was shown by electrical resistance measurements that under pressures near 7.5 kbars and at room temperature, the zinc-blende structure HgSe transformed to a new phase. The transformation was found to be reversible although a distinct hysteresis was encountered. At low temperatures (below 170°K) the high pressure phase of HgSe was retained at atmospheric pressure and was shown by X-ray diffraction techniques to be hexagonal with a = 4.32 A, c = 9.62 A, and a calculated density of 8.95 gms cm 3 .

Nb3In: A β-tungsten structure superconducting compound

High-pressure techniques were employed to synthesize a new compound, Nbain having the β-tungsten structure (A15) with a lattice parameter a0 = 5.303 A. Its superconducting transition temperature was found to be 9.2 ± 0.1°K.

New Phase Transformation in InSb at High Pressure and High Temperature

A new phase transformation at high pressure and elevated temperature has been found in the InSb pressure‐temperature phase diagram. This transformation to a new phase designated as InSb‐III has been established by measurements of superconducting transition temperature (Tc) as a function of annealing temperature at several pressures and by x‐ray determinations on the new phase, both retained at one atmosphere and at high pressure and temperature. The higher Tc for InSb‐III (Tc = 4.1°±0.1°K) and the x‐ray results lead to the conclusion that InSb‐III is a new phase different from the orthorhombic phase (Tc = 3.5°K).

Characteristics of the {111} Surfaces of the III – V Intermetallic Compounds III . The Effects of Surface Active Agents on and the Identification of Antimony Edge Dislocations

The effects of inorganic and organic surface active agents on the behavior of the {111} surfaces in oxidizing etchants were investigated. It was found that specific adsorption of these agents leads to a decrease in the dissolution rate of and pronounced changes in the microstructure of the {111} surfaces. In the presence of an organic sulfide it was possible to develop etch pits which were identified with Sb edge dislocations on the {111} surfaces. This result was verified by means of plastic deformation experiments. Electrical measurements at 78°K suggest that Sb dislocations serve as electron donors whereas In dislocations serve as electron acceptors.

Polymorphism in selenospinels—A high pressure phase of CdCr2Se4☆

Abstract The selenospinel, CdCr 2 Se 4 , has been transformed under high-pressure and temperature to a new structure with monoclinic symmetry related to the defect-NiAs structure and with the lattice parameters: a = 14.62A, b = 6.90A, c = 11.45A, and β = 91.0°. This is consistent with the spinel-to-monoclinic transformations found for the thiospinels, FeCr 2 S 4 , CoCr 2 S 4 , and MnCr 2 S 4 . The high-pressure phase is retained indefinitely at atmospheric pressure and room temperature but retransforms at 125C. The pressure-temperature boundary between the phases has a slope of −15.2°/kbar over the temperature range of 400–750C. Under pressure, the structural change is accompanied by a change from semiconducting to metallic electrical behavior with a drop in resistance from 5 × 10 2 –5.5 × 10 −2 ohms. The magnetic moment at 4.2K decreased from ∼5.6μ B for the spinel phase, which orders ferromagnetically, to ∼0.035μ B for the monoclinic phase, which has weak antiferromagnetic ordering.

High pressure synthesis of arsenopyrite-type ternary compounds

Abstract A series of ternary compounds analogous to FeAsS (arsenopyrite) have been prepared at atmospheric pressure by Hulliger (1, 2) and others (3, 4). They were able to synthesize only 20 of the possible 36 isoelectronic compounds with the general formula MXY, where M is Fe, Ru or Os; X is P, As, Sb or Bi; Y is S, Se or Te. Four of the missing compounds (OsSbSe, OsSbTe, OsBiSe and RuBiSe) have now been synthesized in a tetrahedral anvil high-pressure unit at 35–50 kbar. The role of high pressure is discussed in relation to vapor pressure of the elements, size ratio and compressibility of the atoms, and stability of the phases The X-ray powder patterns of OsSbSe, OsSbTe and OsBiSe have been indexed as monoclinic structures of the same type adopted by Hulliger (2) and the lattice parameters are also consistent. Resistivity measurements on OsSbSe and OsSbTe suggest that they are extrinsic semiconductors.