Effects of additives on perovskite formation in sol-gel derived lead magnesium niobate
Journal
Materials Chemistry and Physics
Journal Volume
62
Journal Issue
1
Pages
18-22
Date Issued
2000
Author(s)
Su, W.-F.A.
Abstract
The effects of ionic compounds (PbO, BaTiO3, PbTiO3, MgO) and covalent compounds (SiO2, GeO2, and B2O3), individually or as mixtures, on perovskite formation in sol-gel derived lead magnesium niobate, PbMg0.33Nb0.67O3 (PMN) were studied. The ionic additives were coprecipitated with the PMN while the covalent compounds were added as fine particulates. At a level of 10 mol% additive per mol of PMN, additions of PbO, BaTiO3, PbTiO3, as alkoxide solutions, increased perovskite formation from 82% to 90, 91 and 87% respectively. A combination of PbO (10-15 mol%) and BaTiO3 (8-9 mol%) increased perovskite formation further to 98%. The addition of 9 mol% MgO alone (also as an alkoxide solution) decreased perovskite formation to 77%, but a combination of PbO (10 mol%) and MgO (5 mol%) increased perovskite formation to 100%. The chemical effects of ionic compounds can be partially explained via the Goldschmidt tolerance factor. Compositions with high tolerance factors (>0.9) exhibited high (>90%) perovskite formation. Additions of 5 mol% GeO2, SiO2, and H3BO3 to modified PMN (14 mol% PbO and 9 mol% BaTiO3), resulted in significant decreases in perovskite formation, from 98% to 86, 80, 50%, respectively, when heated to 980 °C for 8 h. The reduction in perovskite for undoped PMN, however, was nearly double (62% perovskite) when 5 mol% SiO2 was added.
SDGs
Type
journal article