Preparation of Dense BaTiO₃ Ceramics with Submicrometer Grains by Spark Plasma Sintering

Abstract

Dense BaTiO 3 ceramics consisting of submicrometer grains were prepared using the spark plasma sintering (SPS) method. Hydrothermally prepared BaTiO 3 (0.1 and 0.5 µm) was used as starting powders. The powders were densified to more than ≈95% of the theoretical X-ray density by the SPS process. The average grain size of the SPS pellets was less than ≈1 µm, even by sintering at 1000-1200°C, because of the short sintering period (5 min). Cubic-phase BaTiO 3 coexisted with tetragonal BaTiO 3 at room temperature in the SPS pellets, even when well-defined tetragonalphase BaTiO 3 powder was sintered at 1100°and 1200°C and annealed at 1000°C, signifying that the SPS process is effective for stabilizing metastable cubic phase. The measured permittivity was ≈7000 at 1 kHz at room temperature for samples sintered at 1100°C and showed almost no dependence on frequency within ≈10 0 -10 6 Hz; the permittivity at 1 MHz was 95% of that at 1 kHz.

Enhancement of lithium-ion conductivity for Li_2.2C_0.8B_0.2O₃ by spark plasma sintering

“…Detailed employment of the SPS system has been represented in Ref. 18. During SPS process, the operating temperatures reached to 400, 450 or 500°C at a rate of µ50°C/min under argon atmosphere, respectively.…”

“…17) The characteristics of the SPS are not only producing dense pellet but suppressing grain growth by sintering at relatively lower temperature and in shorter periods. Therefore, this technique is very suitable for producing the engineering ceramics functioned by the physical properties at grain boundary as ferroelectric 18) and high-strength materials. 19) In this paper, we attempted to use the SPS process for the enhancement of the lithium-ion conductivity for Li 2.2 C 0.8 B 0.2 O 3 pellet, and compared chargedischarge performance of ASS-LIB assembled by the SPS process to that assembled by conventional furnace sintering (CFS) process.…”

Engrosamiento anormal de partículas submicronicas de BaTiO₃ durante la primera etapa de sinterización

“…La miniaturizaci-n de estos componentes plantea la necesidad de obtener materiales con microestructura homogŽnea y tama-o de grano peque-o. Por lo tanto, la posibilidad de obtener materiales con microestructuras submicr-nicas o nanomŽtricas supone un importante reto de gran trascendencia tecnol-gica (1). Adem ‡s, este tipo de microestructuras puede originar cambios muy significativos en algunas propiedades de interŽs; un ejemplo muy conocido es el caso del BaTiO 3 denso policristalino, en el que una microestructura submicr-nica maximiza la constante dielŽctrica del material y posibilita la fabricaci-n de condensadores m ‡s peque-os (2).…”

Epitaxial Integration of Ferroelectric BaTiO3 with Semiconductor Si: From a Structure- Property Correlation Point of View

“…The idea of the pseudocubic phase is based on a core-shell grain model in which individual grains consist of a cubic shell and a tetragonal grain interior [51]. Internal strains in tetragonal structure caused by the formation of nano-scale grains are believed to be responsible for its change to the so-called pseudocubic phase [52,53]. It can be considered that the obvious ferroelectricity observed in this work for the films after annealing at or above 600 °C is attributed to the formation of the pseudocubic phase, while the strong restrained ferroelectricity for the film annealed at 500 °C is due to the suppression of the tetragonal core caused by the smaller grain size.…”