Photoconductivity in Calcium Tungstate

In view of earlier contradictory published results on the photoconductivity of crystalline calcium tungstate, this effect has been examined using artificial single crystals and an intense ultra-violet source. Photoconductivity has been demonstrated, with a space charge build up of long relaxation time. This latter is probably linked with the long duration phosphorescence previously reported in this material. The evidence produced indicates that calcium tungstate is an intrinsic semiconductor with an activation energy of 2 1 eV. The photoconductive properties are in approximate agreement with the assumption of an exponential trap distribution if a variation of capture cross section with temperature is postulated.