The temperature dependences from 4.2 to 300 K of the seven adiabatic elastic constants of CaWO₄ have been determined by measurements of ultrasound wave velocities using the `sing-around' and pulse superposition methods. The adiabatic elastic constants have been calculated from the measured ultrasound wave velocities by a perturbation method using just seven of the eleven measured velocities and by an iterative method using all the measured velocities; agreement has been found between the two sets of values. The complementary data on the thermal expansion and heat capacity at constant pressure of CaWO₄ have been used with the present results to find the isothermal elastic constants, the heat capacity at constant volume, the Grüneisen parameters, and the Debye characteristic temperature at 0 K. The Debye characteristic temperature has been found from the heat capacity at constant volume from 10 to 300 K after subtraction of the Einstein heat capacity terms from the total heat capacity.

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The energy which must be absorbed in a CaWO₄ x-ray intensifying screen to produce unit net opetical density on a film has been evaluated by measurement and calculation for a screen-film system over a range of beam qualities (1.4--7.4 mm A1 HVL) spanning the diagnostic x-ray region. It was found to be constant within experimental error. The absorbed-energy constant for three additional CaWO₄ screens is presented for a single beam quality. To correct the estimation of absorbed energy, the fractional escape of tungsten K x rays has been evaluated and the results are presented as a function of phosphor loading. The absorbed-energy constant is useful for predicting optical density for variable beam conditions; a family of characteristic curves based on exposure is reduced to one curve for a particular film-screen system, expressed as optical density as a function of absorbed energy.

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A calcium tungstate X-ray phosphor is disclosed which consists essentially of a calcium tungstate host and from about 50 to about 200 parts per million, based upon the weight of the host, of vanadium as a dopant. The disclosed phosphor exhibits no detectable lag or persistence and is appreciably brighter than prior X-ray phosphors. A process for producing the phosphor is also disclosed which process comprises forming an aqueous reaction media of a water-soluble calcium source and a water-soluble tungstate source having an excess of calcium, maintaining a temperature of above about 80°C for a time sufficient to form solid calcium tungstate having a stoichiometric excess of calcium, separating the solid calcium tungstate, adding from about 50 to 200 ppm of a vanadium source and a fluxing material, heating said calcium tungstate to a temperature of between about 700°C and 1150°C for a sufficient time to form a phosphor composition and washing the phosphor with sufficient water to remove any residual water soluble contaminants. An optional process is to add, in addition to the vanadium source, from about 0.05% to about 1.0%, based upon the weight of the host, of tungsten trioxide.

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CaWO₄ single crystals have been grown and compared by three different high temperature solution methods, viz. the normal flux-cooling procedure, the indirect flux-reaction technique and the isothermal flux-evaporation method. The typical as-grown bipyramidal crystals obtained by these methods have been found to be mostly large and perfect with varying degree of transparency. The crystals are characterised by using EDAX, X-ray diffraction, electrical conduction, micromechanical tests and chemical etching. The assessment of various characteristics of the grown crystals is likely to show enormous usefulness of the flux grown crystals.

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