Resistance degradation due to interstitial hydrogen in photorefractive potassium lithium tantalate niobate single crystals

Abstract

Resistance degradation in potassium lithium tantalate niobate (KLTN) doped with iron and titanium was measured in a single sample containing various concentrations of interstitial hydrogen. In this crystal the degradation arose from the migration of interstitial hydrogen and not oxygen vacancies, as reported in previous research. Interstitial hydrogen and oxygen vacancy defects both arise to compensate the valence shortfall of the substitutional iron impurities and the thermodynamic balance between the two compensation mechanisms can be controlled using reaction chemistry techniques. Through appropriate annealing treatments a single crystal of KLTN was prepared in three states: hydrogen-rich oxidized, hydrogen-poor reduced, and hydrogen-rich reduced. The characteristic degradation times for the three cases were 29, 2710, and 26min, respectively. The degradation rate is correlated with hydrogen concentration and not oxidation state of the crystal. Infrared absorption from near the two electrodes of the hydrogen-rich reduced crystal after degradation confirmed polarization of the hydrogen concentration. Electrocoloration was also found to correlate with hydrogen—it was observed in both hydrogen-rich states, but was absent from the hydrogen-poor crystal.

Hydrogen-related dynamic dielectric behavior of barium titanate single crystals

“…Through a well-designed experiment, Ivker et al found that interstitial hydrogen may fulfill the role of mobile ion usually attributed to oxygen vacancy in models of resistance degradation for perovskite-type oxides and a quantitative analysis of the competition between hydrogen and oxygen vacancy was expected. 10 Though oxygen vacancy is ubiquitous in oxide materials, now more and more works have demonstrated that hydrogen also widely exists in many oxides, and as the smallest atom, it deserves extra attention due to its high mobility. 11 In summary, hydrogen from the electrolysis of water induced two kinds of time-dependent changes in dielectric properties of barium titanate single crystals: One was characterized by continuous increases in the slope of capacitancefrequency curve and in the height of a dielectric loss peak in the course of the electrolysis of water; the other was characterized by a continuous decrease in the slope of capacitancefrequency curve and continuous decreases in both the height and the frequency of the dielectric loss peak in subsequent aging process after the electrolysis of water.…”