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The electrical properties of cadmium mercury telluride crystals grown by both a cast-recrystallise and a normal freeze melt growth process have been investigated. Material equilibrated at high temperatures is found to be p-type and the carrier concentration is believed to be determined by native defects. Two models have been considered to explain the carrier concentrations found after low temperature heat treatment of slices in the presence of mercury vapour. These are based on native defects and on residual impurities respectively. It is concluded that for material grown by both growth processes the level of residual impurities is the dominant factor controlling carrier concentration.

An investigation has been carried out into the casting stage of the Cast-Recrystallise-Anneal growth process for crystals of cadmium mercury telluride. The effects of variations in casting rate, directional cooling and thermal insulation of the crucible have been evaluated. Etching and detailed infra-red transmission measurements have been used to assess the resulting material. It is concluded that to achieve uniform composition, material should be cut longitudinally from large diameter crystals. The problems of coring and piping have been alleviated by various techniques but have not been eliminated.

Crystals of cadmium mercury telluride have been grown over a wide range of growth speeds. Both axial and radial compositional variations of the crystals grown have been studied by optical transmission and density measurements. The axial compositional profiles of the slower grown crystals have been compared to the normal freeze complete mixing situation. Radial compositional variations in these crystals can be explained by a boundary layer mechanism. In fast grown crystals, an apparent uniform axial composition is observed while the radial variation can be explained by heat flow considerations.

A simulation model was constructed to compare the profitability of feeding high- and low-protein diets when rearing pullets for egg production. Low-protein diets were found to be more profitable if laying adult birds were subsequently retained beyond 58 weeks of age, although predictions of the model were shown to be very sensitive to some of the inputs and production parameters incorporated in the model. The optimum length of lay for the data being analysed extended beyond 84 weeks of age. This model may be simply modified to study other genotypes and diets than those considered in this paper.

A possible mechanism of crystal growth from the melt is described by which stable facets are assumed to grow by nucleation at the point of critical supercooling, followed by rapid sheet growth across the facet. The velocity of this sheet growth would be independent of the rate of advance of the solid-liquid interface. The mechanism is used as the basis of a mathematical treatment of impurity segregation at a facet, taking into account the adsorption of impurity at the solid-liquid interface. An equation is derived which relates the apparent segregation coefficient at a facet to the velocity of sheet growth and the degree of impurity adsorption. It is shown that, for velocities in the expected range, the value of the segregation coefficient tends to a limiting value which may be greater than 1. The application of the theory to the related problem of dendrite growth is suggested.