Anton V. Polotai

Preparation and Size Effect in Pure Nanocrystalline Barium Titanate Ceramics

The experimental investigation of the rate-controlled synthesis and sintering of barium titanate by different methods have been carried out. It is shown that the permittivity of barium titanate depends on effective grain boundaries width, which consists of physical grain boundary and depolarization field area. The effective grain boundary width depends on ceramics consolidation methods. The polydomain structure with domain width 10-12 nm is discovered in nanocrystalline barium titanate ceramics with grain size 50-70 nm. The generalized polymorphous phase diagram for pure barium titanate is proposed depending on grain size and temperature.

The XRD and IR Study of the Barium Titanate Nano-Powder Obtained Via Oxalate Route

The complex investigation of barium titanyl-oxalate (BTO) thermal decomposition and further synthesis of nanocrystalline barium titanate powder under non-isothermal condition in air at different heating rates has been carried out. It has been revealed that the nucleation of barium titanate phase inside the amorphous intermediate resin-like phase is characterized by latent period, which is independent on heating rates. It is shown that the decomposition process of the initial BTO proceeds through creation of barium carbonate intermediate, which exists in two modifications: unidentate and ionic. XRD and IR characterization of intermediate phases has revealed creation of unstable unidentate barium carbonate during rapid heating and more stable ionic one during slow heating.

Stability of Ni electrodes and Ni-BaTiO3 interface evolution in ultrathin BME MLCCs

Microstructural control in thin-layer multilayer ceramic capacitors (MLCC) is one of the present day challenges for maintaining an increase in capacitive volumetric efficiency. It is observed that the continuity of the Ni electrodes increases with increasing heating rate but behaves non-linearly on sintering temperature. It is proposed that an interfacial liquid alloy layer initiates when the Ni electrodes are under tension. This accelerates a stress-induced diffusion which is the key cause of the severe electrode discontinuities during heating. Kinetic and thermodynamic approaches based on the control of sintering profiles or the control of Ni-BaTiO3 interface chemistry are proposed to prevent the Ni electrode discontinuity.