Synthesis of La and Nb doped PZT powder by the gel-combustion method

Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)(Zr0.60Ti0.40)0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citratenitrate (CA/NO3- 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an autocombustion process at 400 C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2O CO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 C for all citratenitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gelcombustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CANO3 ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.