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Emission spectrum of Tm3+ doped tellurite glasses for the 3H4–3F4 transition at 1.46 μm has been measured at room temperature and at 5 K. The glass compositions have a major influence on the spectral change, especially in the longer wavelength part of the emission. The effect of different Tm3+ concentrations on the upper and lower level lifetimes and on the emission spectrum has also been reported for designing a broadband multi-channel S-band TDFA.

The accuracy of three models for the interpretation of moisture redistribution experiments with fiber glass slabs is investigated. The initial quasi-steady state of the evaporation-condensation process is well predicted by all three models. The quasi-steady model and the numerical model predict much faster changes in the heat flux and temperature distribution during the final drying-redistribution process. The semi-empirical model which incorporates the ‘falling rate’ evaporation period gives more accurate predictions of the experimental data. This model is used to obtain additional physical information on the moisture redistribution and drying process in the slab.

The isothermal viscous flow properties of two fluorozirconate glass compositions have been studied by parallel plate rheometry at temperatures approaching the fibre-drawing viscosity region. An unusual flow behaviour has been found, in which sharp end points occur where deformation ceases under load. This behaviour has been characterised in terms of a threshold yield stress with hysteresis effects. The materials are prone to crystallisation, but no obvious direct link has been found between such effects and the flow behaviour, which may thus be intrinsic.

The use of the technique of parallel plate rheometry for providing viscosity data as a function of temperature in the range 105 to 109 poise is described. Results obtained for a standard reference glass are compared with previous data.

An experimental survey of preparative work in the WO 3 Fe system in which temperatures up to 1100°C and pressures up to 55 kbar have been employed is presented. Two structures not usually found in the WO 3 or FeWO 3 system are encountered. Under the influence of high pressures the concentration of iron in an iron-tungsten bronze phase has been extended beyond the previously known limit of Fe 0.02 WO 3 to approximately Fe 0.1 WO 3 , which has a hexagonal structure with a = 7.422 ± 0.003A, c = 3.766 ± 0.002 A. In the absence of pressure but after long heating times at 1100°C and in the presence of small concentrations of iron, compositions close to W 5 O 14 yield a tetragonal phase a = 23.33 ± 0.01 A, c = 3.797 ± 0.001 A. The details of a single-crystal X-ray structural analysis of this phase are presented which show it to contain pentagonal and hexagonal tunnels and to be isostructural with Mo 5 O 14 as seen in |001| projection. The space group is identified as P 42 1 m which is different from that of Mo 5 O 14 . The difference between W 5 O 14 and Mo 5 O 14 is seen in the presence of less severe puckering and a simpler arrangement of the metal atoms about z = 1 2 which does not give rise to a superlattice cell hence leading to the observed difference in space group.

The technique of microhardness measurements using diamond indenters is outlined and assessed for its potential use in quantifying bonding changes and studying reactions in nonstoichiometric crystals. Results are presented for both Vickers and Knoop hardness values on {001} and {011} crystal planes of cubic sodium tungsten bronzes, NaxWO3, with x in the range 0.5 to 0.75. The Knoop data show that in only one direction, 〈110〉 on {001}, is the hardness sensitive to changes in composition. Hardness in the 〈110〉 directions and the degree of anisotropy increase as the sodium content of the bronze increases. All the crystal faces examined showed marked anisotropic behavior, with 〈110〉 being about 50% harder than 〈100〉 on {001} faces, while on {011} planes hardness increases in the sequence 〈100〉:〈211〉:〈111〉 ≈ 〈011〉. Hardness results from isomorphous and isoelectronic ReO3 are considered with the NaxWO3 data to show the dominant role played by Na+WO3 matrix interactions in determining the properties of these materials. The results are discussed in terms of current bonding theories for bronzes.

The electronic expansion factor for bronze phases with the perovskite structure are derived from a wide variety of literature sources and shown to fit a curve when plotted against the Ahrens ionic radius of the non-network-forming cations. Examples are given which show how the curve can be used to characterize and compare bronze-like phases.

The reaction of the cubic sodium bronzes, NaxWO3, with powdered iron metal has been studied by heating samples in vacuo and also at high pressure. Evidence for reaction is found at unexpectedly low temperatures. The reaction is an overall reduction which proceeds via an increase in the sodium content of the bronze phase up to some temperature-dependent limiting composition for which x < 1. The existence of this limit, its temperature dependence, and the identity of the other products of reduction have been explained in terms of the partial oxygen pressure of the system. The course of the reduction has been followed through the evolution of the bronze lattice parameter and a reaction mechanism is postulated. No evidence of significant incorporation of iron into a stable cubic sodium bronze phase has been found.

Electron microscopic observations of microstructure, together with studies of the evolution of X-ray and electron diffraction patterns, have been used to provide mechanistic information on the dehydration of boehmite to γ-Al 2 O 3 . Firing boehmite in air at 400°C produces slow development of a fine, lamellar, porous microstructure, oriented parallel to (001) γ , the dimensions of which are consistent with the loss of one-quarter of the oxygen atoms of the boehmite lattice. The mechanism proposed for the dehydration is controlled by diffusion in a direction determined by the hydrogen bond chains in the boehmite structure and involves countermigration of the Al cations and protons with crystallographic formation of voids in a coherent cubic close-packed matrix. Final reorganization to give the spinel structure of γ-Al 2 O 3 is suggested to involve gradual filling of the tetrahedral cation sites.

The technique of parallel plate rheometry has been used to study the viscosity-temperature characteristics of candidate glasses for use in infrared transmitting optical fibres.

A time-temperature study has been made of the system: γ- AlOOH (boehmite) Al 2 O 3 . The isothermal TTT diagram produced demonstrates the course of the transformation sequence, which involves a number of metastable transition alumina intermediate phases. This type of treatment allows calculation of kinetic parameters for the various transformation processes, and these may be correlated with the mechanisms operating. Kinetic aspects of variations in microstructure and crystal structure have also been studied. In particular, the progress of cation migration processes involved in the transformation γ → δ-Al2O3 has been followed in terms of the continuous variation of the spinel subcell parameters.

We point out an error in a recent paper by Lerche and Low [3] and show that the claimed temperature inversion with a local maximum at the centre cannot take place in their model where the radiative rate of cooling is of the form ϱS(p), ϱ being the density and S(p) a monotonically increasing function of the pressure p.