SOME PROPERTIES OF SEMICONDUCTING COPPER-CALCIUM-PHOSPHATE GLASSES.

In the examination of a range of glasses containing up to 35% of Cu as a replacement for Ca, the optical absorption edges are measured and analyzed in terms of forbidden non-direct transitions across an optical energy gap which is found to increase linearly with the Cu content of the glasses. Values of E//o//p//t in the range 1. 56 to 1. 85 eV are compared with electrical activation energies in the range 2. 20 to 2. 48 for the same glasses. The distribution of the copper between the two main valency states is determined by measurements of electron spin resonance arising from the Cu**2** plus centers. The study of e. s. r. at room and low temperatures provides further evidence for hopping conduction in the glasses. Electron diffraction data show evidence for a phase transformation during switching.