Phase formation of ferroelectric perovskite 0.75 Pb(Zn1/3,Nb2/3)O3–0.25 BaTiO3 prepared by aqueous solution–gel chemistry

Abstract

Here we report on the synthesis and phase formation of perovskite 0.75 Pb(Zn 1/3 ,Nb 2/3 )O 3 -0.25 BaTiO 3 (PZN-BT) by means of a new aqueous solution-gel method. The gelation process was optimized for an ammonium PZN acetate citrate precursor. The chemical homogeneity of this precursor was investigated by means of TEM-EDX analysis (Transmission Electron Microscopy-Energy Dispersive X-ray analysis). All metal ions were found to be homogeneously dispersed in the precursor gel at least down to 10 nm. An aqueous BaTiO 3 precursor was synthesized and its oxide formation was investigated by means of HT-XRD (High Temperature X-ray Diffraction) and TGA-MS (Thermogravimetric Analysis on-line coupled to Mass Spectrometry). The gel-to-oxide transition of the PZN-BT precursor was studied using HT-XRD and TGA-MS. It was concluded that 96z weight% perovskite PZN-BT could be formed out of the gel precursor if proper thermal treatment is applied (14 minutes sintering at 800 ‡C after fast firing at 50 ‡C min 21 ). Finally a phase formation mechanism for perovskite PZN-BT is proposed: perovskite 0.75 Pb(Zn 1/3 ,Nb 2/3 )O 3 -0.25 BaTiO 3 is formed out of a cubic pyrochlore PZN. At 850 ‡C the perovskite decomposes irreversibly into that same pyrochlore together with volatile PbO and ZnO. The evolution of PbO was proved with TGA.

Progress in synthesis of ferroelectric ceramic materials via high-energy mechanochemical technique

“…For example, a new aqueous solution-gel method was recently developed by Werde et al to synthesize perovskite 0.75PZN-0.25BT [159], where PZN acetate citrate precursor was combined with an aqueous BT precursor. Although high chemical homogeneity was found in the mixture, the maximum weight percentage of perovskite was 96%, which was only achieved under proper thermal treatment (14 min calcination at 800°C after at fast firing rate of 50°C/min).…”

Synthesis and characterization of NiO and nanoparticles obtained by a sucrose-based route

“…Among the several methods, the ones that keep a high random distribution of the metal ions or complexes are based on the use of a matrix (solution, gel or ''resin''). This characteristic increases the chemical homogeneity and avoids (or reduces) the segregation of a particular metal during the processing and crystallization of the multimetal oxides [7][8][9]. In these chemical methods, the metal ions (or complexes) are immobilized on an atomic scale (inside the matrix), which allows to obtain oxides at temperatures lower than the ones produced in solid state reaction.…”

“…In these chemical methods, the metal ions (or complexes) are immobilized on an atomic scale (inside the matrix), which allows to obtain oxides at temperatures lower than the ones produced in solid state reaction. Due to the immobilization, the metal ions react with each other with a minimum diffusion; consequently, it is possible to synthesize homogeneous and stoichiometrical oxides [7,8]. Sol-gel techniques are well known examples of routes with these characteristics [10,11].…”

Pyrochlore‐Free Ferroelectric 0.64Pb(Ni1/3Nb2/3)O3–0.36PbTiO3 Ceramics Synthesized by the Combustion Method

“…When temperature increased, the polymerized organic chains began decomposing into metallic‐organic chain segments or oligomers, and decomposed subsequently into mixed oxide phase above 460°C . According to Chaput and Werde‘s reports, the pyrochlore phase will form from the reaction of PbO and Nb 2 O 5 below 450°C. For our combustion method, the PbO and Nb 2 O 5 formed above the formation temperature of the pyrochlore phase.…”