Nonuniformities in the air-sweeping of quartz

The mechanism for electrode void formation before and during sweeping that leads to nonuniform H-sweeping is discussed. The conditions that restrict H-introduction and allow nonuniformities to develop are described. The techniques and electrode types available to circumvent the restriction of uniform hydrogen indiffusion are presented. Experimental methods and observations are discussed. It is found that stress-induced voiding of evaporated metal electrodes normally provides openings (electrode-quartz-water vapor regions) that allow the indiffusion of hydrogen for sweeping. The voiding is influenced by metal particle size and the application of compressive stresses. Since the extensive stress-induced voiding necessary for uniform sweeping is difficult to control, sufficient open electrode regions can be created artificially to ensure uniform H-sweeping. Uniform H-sweeping can be achieved by using conducting oxide electrodes that permit the diffusion of hydrogen without the need for electrode porosity