Effect of humidity on dielectric properties of lead magnesium niobate containing excess MgO

The enhancement of dielectric constant (K) in humid atmosphere (K-max = 133 60 in dry atmosphere to 17450 in 100% relative humidity) for lead magnesium niobate [Pb(Mg1/3Nb2/3)O-3] relaxor materials sintered at 950 degrees C fo r 30 min (using 3 wt% excess Pbo as a sintering aid) can be explained by th e extended low frequency dispersion (LFD) model proposed earlier. However, it has been observed that for samples containing excess MgO, such enhanceme nt of K-max in humid atmosphere is not so remarkable. It has been shown tha t in case of samples containing excess MgO, owing to the presence of alread y formed OH- ions at the surface arising out of the reaction of adsorbed mo isture with MgO, the physical absorption of polar H2O molecules in humid at mosphere will be much less and consequently the enhancement of dielectric r esponse in humid atmosphere should be low. (C) 2000 Elsevier Science Ltd. A ll rights reserved.