EFFECT OF ATMOSPHERE ON STABILITY OF PB(MG1 3NB2/3)O-3 (PMN) CERAMICS/

The effect of atmosphere on the chemical stability of Pb(Mg1/3Nb2/3)O- 3 (PMN) ceramics at high temperature was examined. Heating the PMN pel let in air caused PbO vaporization to decompose PMN into a pyrochlore- type compound and Mg4Nb2O9 from surface toward the bulk. The decomposi tion rate was controlled by the Pb diffusion rate. The surface layer c onsisting of pyrochlore-type compound and Mg4Nb2O9 significantly lower ed the dielectric constant. The PMN pellet after decomposition was hea ted again under PbO vapors produced by a powder mixture of PbO and ZrO 2. Consequently, it was found that the pyrochlore-type compound and Mg 4Nb2O9 reacted with PbO to form PMN from surface toward the bulk. This indicates that the decomposition reaction is reversible by the transp ortation of PbO from surface into the bulk. Copyright (C) 1997 Elsevie r Science Ltd.