Phase transformation and densification behavior of La-modified lead metaniobate ceramics

The phase transformation and densification behavior of (Pb1-X2+La2X/33+)(5) Nb10O30 (X = 0.00-0.20) tungsten bronze (TB)-type compounds were studied wi th respect to La3+ ion substitution for Pb2+ ion in Pb5Nb10O30 Analysis of the phase identification shows that the phase transformation temperature (l ow temperature rhombohedral form <----> high temperature tetragonal form) d ecreases along with the increase of La"' amount. The decrease of phase tran sformation temperature limits excessive grain growth,, which usually occurs from the co-proceeding of phase transformation and sintering in Pb5Nb10O30 and, as a result, the density after sintering is effectively improved. Fur thermore, two different densification models for Pb5Nb10O30 and (Pb-1-X(2+) La-2X/3(3+))(5)Nb10O30 Were described and discussed.