Influence of synthesis and processing parameters of the columbite precursor on the amount of Perovskite PMN

Abstract

Columbite route for synthesis of P3MgNb2O9 (PMN) allows the suppression of secondary phases in PMN powders. These phases, having low dielectric constant, affect negatively the dielectric properties of PMN ceramics. Aiming to get reactive PMN powders, the partial oxalate method was used to precipitate lead oxalate over MgNb2O6 particles. The columbite (NM) powders were prepared using polymeric precursor based on Pechini's method. Two processing routes were used to prepare PMN powders. In the first one the NM-lead oxalate co-precipitate was washed in water and ethanol and calcined at several temperatures. In the second route, the NM-lead oxalate co-precipitate was washed in water and isopropyl alcohol, ball milled for 30 min and calcined at several temperatures. The second route leads to practically pyrochlore free PMN. Powders morphologies observed by SEM showed the formation of agglomerates, which sizes depend on the processing route.

Effect of PbO excess on the formation of lead magnesium niobate perovskite by the columbite method

“…In order to prepare PMN powders, the partial oxalate method was used. The co-precipitates were decomposed at 400 • C for 2 h in air flux and heat-treated at 800 • C for 2 h in alumina crucibles [10,13]. From a basic composition of PMN, four different powder batches having different amounts of PbO excess (0-3 wt.%) were prepared.…”

“…PbO volatilization is the main occurrence factor when the pyrochlore amount increases in PMN powders, and in this way, many artifices can be used to avoid the formation of the pyrochlore phase [12][13][14]. PbO excess is one of them, because it aims to compensate PbO volatilization during heat treatment [15][16][17].…”

Study of microstructure and dielectric properties of PMN–PZT ceramics via a mixed powder method including sol–gel precursor

“…activation [7,8] or sol-gel [9][10][11] methods. Synthesis of single phase PMN requires more specified processing routes, such as columbite route [12][13][14][15], mechanical activation process [16][17][18], reaction sintering process [19][20][21] and sol-gel method [22,23]. There are also more routes proposed by other authors for PMN-PZT production such as mixed oxide method [24], columbite or corundum routes [25] and wet chemical routes [26,27].…”

Effect of sintering conditions on the pyrochlore phase content in PMN–PFN ceramics prepared by sol–gel process

“…Ananta and Thomas 11 developed two-stage mixed oxide synthetic routes for the preparation of single phases of lead-based complex perovskite PMN and PFN and two complex perovskite compounds at selected compositions in the PMN-PFN pseudo-binary system were prepared and characterized 12 . PMN is also synthetized by various wet chemical processing routes such as sol-gel, 9,[13][14][15][16] combustion synthesis, 17,18 coprecipitation, 19 molten salt synthesis, 20 citrate gel, 21,22 partial oxalate, 23,24 polymerized complex, 24,25 citrate complex 26 and a niobium tartarate complex 27 methods. The combination of the partial oxalate method with the columbite route and the Pechini method was used to obtain PMN powder at low temperature.…”