Platelike Bi4Ti3O12 Particles Research Articles

Plate-Like Bi4Ti3O12 Particles and their Topochemical Conversion to SrTiO3 Under HydrothermalConditions

Plate-like Bi 4 Ti 3 O 12 particles were synthesized using a one-step, molten-salt method from Bi 2 O 3 and TiO 2 nanopowders at 800 °C. The reaction parameters that affect the crystal structure and morphology were identified and systematically investigated. The differences between various Bi 4 Ti 3 O 12 plate-like particles were examined in terms of the ferroelectric-to-paraelectric phase transition and the photocatalytic activity for the degradation of Rhodamine B under UV-A light irradiation. The results encouraged us to conduct further testing of the as-prepared Bi 4 Ti 3 O 12 plate-like particles as templates for the preparation of plate-like SrTiO 3 perovskite particles using a topochemical conversion under hydrothermal conditions. The characteristics of the Bi 4 Ti 3 O 12 plates and the reaction parameters for which the SrTiO 3 preserved the shape of the initial Bi 4 Ti 3 O 12 template particles were determined.

Enhanced piezoelectric properties and strain response in 〈001〉 textured BNT-BKT-BT ceramics

Highly 〈001〉 textured (~81%) ternary BNT-BKT-BT ceramics are prepared by reactive templated grain growth (RTGG) method with plate-like Bi4Ti3O12 particles as templates. Outstanding electric properties, which are both higher than state of art BNT-based ceramics, emerge in the aforementioned sample due to the grain orientation. For the textured ceramics, a high piezoelectric constant d33 of 314pC/N could be obtained, which is ~1.4-fold larger than that of a random one (221pC/N). A high electro-strain response (~0.41%) is obtained at a low applied electric field (4kV/mm) in textured ceramics, with the normalized strain d33⁎ (Smax/Emax)=1030pm/V near the TF-R (the temperature of ferroelectric to ergodic relaxor state transition). Moreover, the evolution process of relaxor phases is studied. The texture technique also could improve the TF-R from 70°C to 100°C, enhancing the temperature stability. In addition, the polarization switching process in ferroelectric phase and ergodic relaxor state are analyzed in this work, respectively.

Formation Mechanism of Plate-like Bi4Ti3O12 Particles in Molten Salt Fluxes

The plate-like Bi4Ti3O12 particles were prepared by molten salt synthesis method. The influence of sintering temperature and cooling process on the microstructure of Bi4Ti3O12 powders was studied. Much larger particles were formed at higher temperatures. The particles could grow larger in slow cooling process. The formation mechanism of plate-like Bi4Ti3O12 particles in Na2SO4-K2SO4 system could be viewed as four processes: (1) solid reaction and nucleation, (2) plate-like structure formation, (3) diffusion and edge nucleation, (4) diffusion and epitaxial growth.

Electrical Properties of Textured (Bi1/2K1/2)TiO3–BaTiO3 Lead-Free Piezoelectric Ceramics

The electrical properties of (1-x)(Bi1/2K1/2)TiO3–xBaTiO3 (BKT–BT100x) ceramics prepared by an ordinary solid-state reaction and a reactive templated grain growth (RTGG) method using platelike Bi4Ti3O12 particles as a template were investigated. The degree of orientation, F, which was determined by the Lotgering method using an X-ray diffraction pattern, achieved ≈83% in the textured BKT–BT10 ceramic. A textured BKT–BT10 ceramic with a homogeneous microstructure was obtained after a long sintering time. The field-induced strains and piezoelectric properties of the BKT–BT10 ceramic were improved by improving grain orientation. In particular, the piezoelectric strain constant, d33, and the normalized strain, d33*, of the textured BKT–BT10 ceramic in the direction parallel (∥) to the tape stacking direction were 121 pC/N and 211 pm/V (at 80 kV/cm), respectively.

Control of Microstructures of Textured (Bi1/2K1/2)TiO3-BaTiO3 Ceramics

Control of the microstructures of (1–x)(Bi1/2K1/2)TiO3-xBaTiO3 (x = 0.1) [abbreviated as BKT–BT10] ceramics prepared by a reactive templated grain growth (RTGG) using platelike Bi4Ti3O12 particles as a template were investigated. All samples showed a single-phase perovskite structure. The degree of orientation F, which was determined by the Lotgering method using X-ray diffraction pattern, achieved only ∼ 60% in textured BKT-BT10 ceramics. Textured BKT-BT10 ceramics with a homogeneous microstructure were obtained by the the longer sintering time. It is very important to perform long sintering in order to promote the grain growth and improve the orientation factor for this composition.

Effect of Template Particle Formation on Texture Development in Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub> Ceramics

The factor determining texture development was examined for Bi0.5Na0.5TiO3 ceramics made by the reactive-templated grain growth process using platelike Bi4Ti3O12 particles as reactive template. Platelike, skeleton Bi0.5Na0.5TiO3 particles were formed by the reaction between Bi4Ti3O12 and Na2CO3 in calcined compacts. Coalescence of small grains in the skeleton particles to form single template particles was important to obtain highly textured ceramics.

Fabrication and Piezoelectric Properties of Grain-Oriented (Bi1/2K1/2)TiO3–BaTiO3 Ceramics

The piezoelectric properties of (1 - x)(Bi1/2K1/2)TiO3–xBaTiO3 (x = 0.1) [abbreviated as BKT–BT10] ceramics prepared by ordinary solid-state reaction and reactive templated grain growth (RTGG) using platelike Bi4Ti3O12 particles as a template were investigated. All samples showed a single-phase perovskite structure, and relative densities compared with theoretical densities were all higher than 95%. The degree of orientation F was determined by the Lotgering method using an X-ray diffraction (XRD) pattern. The F values of textured BKT–BT10 ceramics were relatively low at ∼35%. However, field-induced strains and piezoelectric properties of BKT–BT10 ceramics were improved by grain orientation. In particular, the piezoelectric strain constant d33 and the strain of textured BKT–BT10 ceramics in a direction parallel (∥) to the tape stacking direction were 84.5 pC/N and 168 pm/V (at 80 kV/cm), respectively.

Preparation of Textured Bi0.5(Na,K)0.5TiO3-BiFeO3Solid Solutions by Reactive-Templated Grain Growth Process

Textured Bi 0.5 (Na,K) 0.5 TiO₃-BiFeO₃ ceramics were prepared by the reactive-templated grain growth process, using platelike Bi4Ti₃O₁₂ particles. The effects of chemical composition in Bi 0.5 (Na,K) 0.5 TiO₃ on texture development and densification were examined. Textured ceramics were obtained by using Bi 0.5 K 0.5 TiO₃ as an end member of the solid solution but densification was limited. Dense ceramics were obtained by using Bi 0.5 Na 0.5 TiO₃ but texture did not develop. Dense, textured ceramics were obtained by using Bi 0.5 (Na 0.5 K 0.5 ) 0.5 TiO₃.

Anisotropic Properties of Grain Orientated Bismuth Titanate Ceramics by Spark Plasma Sintering

Textured bismuth titanate ceramics were successfully produced by spark plasma sintering, using plate-like Bi4Ti3O12 particles prepared by a molten salt method. The microstructure and electric properties of the samples were investigated. The results show that the textured Bi4Ti3O12 ceramics electric property is anisotropic in different direction, and spark plasma sintering is an effective sintering technology to get textured dense Bi4Ti3O12 ceramics at a low temperature.

Factors Determining Grain Orientation in Bismuth Sodium Potassium Titanate-Lead Zirconate Titanate Solid Solutions Made by the Reactive Templated Grain Growth Method

Grain-oriented Bi0.5(Na0.85K0.15)0.5TiO3-Pb(Zr1−xTix)O3 (BNKT-PZT) ceramics were prepared via the reactive templated grain growth method, using platelike Bi4Ti3O12 particles. Factors that determine the degree of orientation were examined. Prereacted PZT gave a larger degree of orientation than PZT raw materials (PbO, ZrO2, and TiO2) in the 75BNKT-25PZT (x= 0.5) system. Increases in the titanium concentration in the PZT of the 75BNKT-25PZT system and in the BNKT concentration in the yBNKT-(100 −y)PZT (x= 0.5) system increased the degree of orientation. The direction of material transport between BNKT and PZT was important to obtain ceramics with a large degree of orientation.

Effect of Potassium Concentration on the Grain Orientation in Bismuth Sodium Potassium Titanate

Bi0.5(Na1‐xKx)0.5TiO3 (BNKT) bulk ceramics with a preferred <100> orientation were prepared using the reactive templated grain‐growth method with platelike Bi4Ti3O12 particles as templates for BNKT. The potassium concentration (x value) had a large effect on the degree of orientation, and highly oriented ceramics were obtained for the specimens with x= 0.10 and x= 0.15, whereas the specimen with x= 0.00 had a small degree of orientation. Increased potassium concentration from x= 0.00 to x= 0.15 decreased the grain‐growth rate and changed the grain shape from irregular to cubic. These factors were responsible for the increased degree of orientation.

Particle Orientation During Tape Casting in the Fabrication of Grain‐Oriented Bismuth Titanate

Slurries containing platelike Bi4Ti3O12 particles have been tape cast to prepare green sheets with aligned particles. The slurries contain well‐dispersed particles and show nearly Newtonian flow behavior. The effect of slurry composition and casting conditions on the particle orientation has been examined. The particle orientation in the green sheet is determined mainly by powder content; other parameters, such as binder content, casting speed, and blade opening, have little effect. The interaction between particles is a main cause for particle alingnment. The slurry with a large powder content is favorable for preparing dense grain‐oriented ceramics.