摘要:

From an electron-diffraction study the crystalline c-phase, observed together with the quasicrystals in an Al─Li─Cu─Mg alloy, has been analysed as exhibiting an almost perfect icosahedral symmetry. Orientation relationships with quasicrystals are determined and serve to define a new class of approximant structures, including, beyond the c-phase, the Ti2Ni and Ti2Fe structures.

ISSN:0950-0839    

DOI:10.1080/09500838708214703

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The mean velocities of α, β and screw dislocations in doped GaAs have been determined by X-ray topography. Although the velocities of β dislocations were found to be nearly equal to those measured in undoped material, the velocities of α and screw dislocations were lower. The activation energies for dislocation motion were found to be approximately the same as in undoped material, except for temperatures higher than 400°C and values of the resolved shear stress, σ, less than 10 MPa. In this range, the mobilities of α and screw dislocations were more severely reduced and were time-dependent. We suggest that these different effects are related to a selective interaction between the dopant (In) and α partials.

ISSN:0950-0839    

DOI:10.1080/09500838708214704

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Observations of beam damage under high-current-density irradiation in three forms of titanium oxide are presented. The three forms: TiO2, Ti2O3and TiO, have widely differing electrical conductivities but all appear to be damaged by the same mechanisms. The results are discussed in terms of a previously reported model which suggested that only ionic insulators should be susceptible to this type of damage.

ISSN:0950-0839    

DOI:10.1080/09500838708214705

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We describe a new method of computer simulation which combines the methods of lattice statics and Monte Carlo importance-sampling. The method is illustrated with a calculation of the zero-Kelvin or configurational chemical potential in the linear deformable lattice gas.

ISSN:0950-0839    

DOI:10.1080/09500838708214706

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The electrical resistivity of bulk semiconducting amorphous TlxSe100−xalloys with 0 ≤ x ≤ 25 has been investigated up to a pressure of 14 GPa and down to liquidnitrogen temperature by use of a Bridgman anvil device. All the glasses undergo a discontinuous pressure-induced semiconducting-to-metal transition. X-ray diffraction studies on the pressure-recovered samples show that the high-pressure phase is the crystalline phase. The pressure-induced crystalline products are identified to be a mixture of Se having a hexagonal structure witha= 4·37 Å andc= 4·95 Å and TlSe having a tetragonal structure witha= 8·0 Å andc= 7·0 Å

ISSN:0950-0839    

DOI:10.1080/09500838708214707

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We find that the photo-induced excess conductivity (persistent photoconductivity, PPC) in doping-modulated hydrogenated amorphous silicon (a-Si: H) is thermally activated for exposure temperatures above 220 K in agreement with Kakalios and with Hundhausen and Ley. However, we find a temperature regime between 80 and 220 Kin which the PPC measured at 300 K is independent of excitation temperature. Whether the PPC is excited in the thermally activated regime above 220 K or in the temperature-independent regime, the annealing occurs at 410 K. The pre-exponential factor and the activation energy of PPC are related by the Meyer-Neldel rule independent of the excitation temperature.

ISSN:0950-0839    

DOI:10.1080/09500838708214708

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A mixed mechanical-computer model was used to obtain information about the medium range order in amorphous As2S3. Beginning with a mechanical stick and ball model, the structure was computer relaxed with an interatomic potential. The relaxed model shows evidence of polymeric non-planar structural ordering.

ISSN:0950-0839    

DOI:10.1080/09500838708214709

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor