Lead oxide based ferroelectric and piezoelectric ceramics, represented by lead zirconate titanate (PZT), are widely used for piezoelectric actuators, sensors and transducers. However, volatilization of toxic PbO during high-temperature sintering causes environmental pollution. Therefore, it is necessary to develop environment – friendly lead-free piezoelectric ceramics.

Sodium bismuth titanate Na_0.5Bi_0.5TiO₃ (NBT) and potassium bismuth titanate K_0.5Bi_0.5TiO₃ (KBT) are very useful candidates of lead-free piezoelectric ceramics. NBT and KBT powders are traditionally prepared by solid-state reaction via the calcinations of metal oxide or carbonate powders.

The goal of the present work was to investigate the formation of NBT and KBT at low temperatures and at short times using the molten salt method. The first stage of the study related to obtaining NBT and KBT using Bi₂O₃, TiO₂, Na₂CO₃ and K₂CO₃ as starting raw materials. The second stage included obtaining NBT and KBT from intermediate binary compound Bi₄Ti₃O₁₂ and TiO₂, Na₂CO₃ and K₂CO₃, respectively. The precursors were mixed with a mechanically driven agate mortar and pestle for 1h. The mole fractions of NaCl and KCl were equal. Equal weight mixtures of salts and precursors were used. The mixed powders were heated to temperatures of 800 to 1000ºC in a covered alumina crucibles for the desired time. After thermal treatment the salts were remove by washing with deionized water several times. The morphology of the powders obtained was examined by SEM. Phases present were determined by XRD.

It has been found, that molten salt synthesiss of NBT and KBT is one low-temperature route which has been of considerable interest. It allows melt-solid reactions which are much faster due to small diffusion distances and higher mobility of oxides in the melt. The powder particles with an anisotropic shape were prepared by using a starting precursor Bi₄Ti₃O₁₂ with an anisotropic shape.

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1. Anisotropic grain growth of bismuth titanate in molten salt fluxes
2. Use of X-ray powder diffraction method for study on synthesis and decomposition of K₂Ti₈O₁₇
3. Molten salt synthesis and characterization of Bi₄Ti₃O₁₂ crystals
4. Investigations on synthesis and microstructure of potassium titanates