Effects of heat treatment and Cu 2O content of lead aluminoborate glasses on their conduction mechanisms and microhardness

Abstract

The following glass compositions were prepared: PbO·(76 − x)B 2O 3·(10)Al 2O 3( x)Cu 2O, where X = 0.1, 0.3, 0.5, 0.7, 1.0 and 1.5 mol%. The structural analysis were carried out using: (1) X-ray diffraction; (2) differential thermal analysis (DTA), and (3) infrared spectroscopy (IR). Cu 2O additives increased the thermal stability of the present glasses. The obtained DTA transition temperatures and IR absorption bands are similar to those characterizing the lead aluminoborate glasses. However, the T g values of some separated phases increased as the Cu 2O content was increased. The microhardness behaviour as a function of Cu 2O content exhibited a broad minimum around 0.5–1 mol%. Three temperature regions were obtained from the resistivity (ϱ)-temperature ( T) dependence in the range of 353–573 K): (1) the low temperature region, which was characterized by an electronic variable range hopping mechanism; (2) the transition region, for which a compensation model was suggested to explain mathematically and physically the conduction mechanism; and (3) the high temperature region (HTR), which was controlled by Arrhenius equation, and Pb 2+ acted as a charge carrier. For HTR both the activation energy E and log ϱ (measured at 526 K) increase as the Cu 2O content increases. This result was attributed to the formation of Cu clusters. The tempering temperature dependence of E and log ϱ revealed peaks at 380°C which were ascribed to the early stage of spinodal decomposition at this temperatures.