Effect of Constituent Core-sizes on Microstructure and Dielectric Properties of BaTiO₃@(0.6Ba-TiO₃-0.4BiAlO₃) Core-Shell Material

Abstract

The fundamental characteristics of varied initial core-sizes of BaTiO₃(BT) and its influential role on the morphology and dielectric properties of BaTiO₃@0.6BaTiO₃-0.4BiAlO₃(BT@0.6BT-0.4BA) ceramic samples were studied. Alkoxide sol-precipitation method was adopted as revised chemical route to synthesize the constituent “core” BT powders in a dispersed phase, whereas the distinctive initial nano-sized particles were affected by the pre-calcination temperatures (600-900 °C).The microstructure of the uncoated BT ceramics revealed an exaggerated grain growth with an optimized dielectric constant (ε _max >9 000) whilst the coated ceramics behaved otherwise (grain growth inhibited) when sintered at an elevated temperature. Regardless of the previously studied solubility limit (about 0.1%) of BT-BA samples, BT@0.6BT-0.4BA maintained a maximum dielectric constant (ε _max) ranging from 1 592 to 1 708 and tan δ less than 2% under a unit mole ratio at room temperature. In view of all these analyses, the initial nanometer sizes of the as-prepared BT-core powders combined with the increase effect of cation substitutions of Bi³⁺ and Al³⁺ in the shell content, induced the diffuse transition phase of BT@0.6BT-0.4BA composition.

Keywords

MLCCs / core-shell / Alkoxide sol-precipitation / relaxor / grain boundary segregation

References

[1] Chen K Y, Huang C W, Wu M, et al. Advanced Characterization of Mechanical Properties of Multilayer Ceramic Capacitors[J]. J. Mater. Sci. Mater. Electron., 2014, 25: 627-634.

[2] Badheka P, Qi L, Lee B I. Phase Transition in Barium Titanate Nanocrystals by Chemical Treatment[J]. J. Eur. Ceram. Soc., 2006, 26: 1393-1400.

[3] Liu Y, Cui B, Wang Y, et al. A Novel Precipitation-Based Synthesis for the Formation of X8R-type Dielectrics Composition Based on Monodispersed Submicron Ba_0.991Bi_0.006TiO₃@Nb₂O₅ Particles[J]. J. Eur. Ceram. Soc., 2015, 35(9): 2461-2469.

[4] Zhao Z, Buscaglia V, Viviani M, et al. Grain-size Effects on the Ferroelectric Behavior of Dense Nanocrystalline BaTiO₃ Ceramics[J]. Phys. Rev. B, 2004, 70(2): 024107

[5] Vijatovic MM, Bobic JD, Stojanovic BD. History and Challenges of Barium Titanate: Part 1[J]. Sci. Sinter., 2008, 40: 155-165.

[6] Zhang X, Wang X, Tian Z, et al. Synthesis of Monodispersed Barium Titanate Nanoparticles with Narrow Size Distribution by a Modified Alkoxide-Hydroxide Sol-Precipitation Method[J]. J. Am. Ceram. Soc., 2010, 93(11): 3591-3594.

[7] Potdar H S, Deshpande S B, Date S K. Chemical Coprecipitation of Mixed (Ba+Ti) Oxalates Precursor Leading to BaTiO₃ Powders[J]. Mat. Chem. Phys., 1999, 58: 121-127.

[8] Rawal B S, Kahn K, Buessem W R. Grain Core-Shell Structure in Barium Titianate-Based Dielectrics[J]. J. Am. Ceram. Soc., 1981, 1: 172-188.

[9] Liu G, Wang X H, Lin Y, et al. Growth Kinetics of Core-shell-Structured Strains and Dielectric Constant in Rare-Earth-Doped BaTiO₃ Ceramics[J]. J. Appl. Phys., 2005, 98(4): 044105

[10] Liu M, Hao H, Zhen Y, et al. Temperature Stability of Dielectric Properties for xBiAlO₃-(1-x)BaTiO₃ Ceramics[J]. J. Eur. Ceram. Soc., 2015, 35: 2303-2311.

[11] Liu M, Hao H, Chen W, et al. Preparation and Dielectric Properties of X9R Core–Shell BaTiO₃ Ceramics Coated by BiAlO3-BaTiO₃[J]. Ceram. Int., 2016, 42: 379-387.

[12] Wang T, Hao H, Liu M, et al. X9R BaTiO₃-Based Dielectric Ceramics with Multilayer Core–Shell Structure Produced by Polymer-Network Gel Coating Method[J]. J. Am. Ceram. Soc., 2015, 98: 690-693.

[13] Yeith M, Mathur S, Lecerf N, et al. Sol-Gel Synthesis of Nano-Scaled BaTiO₃, BaZrO₃ and BaTi_0.5Zr_0.5O₃ Oxides via Single-Source Alkoxide Precursors and Semi-Alkoxide Routes[J]. J. Sol-Gel Sci. Techn., 2000, 17(2): 145-158.

[14] Hessien M M, El-Bagoury N, Mahmoud M H H, et al. Synthesis and Characterization of Nanocrystalline Barium-Samarium Titanate High[J]. High Temp. Mater. Proc., 2015, 35(5): 499-505.

[15] Yu H, Ye Z G. Dielectric Properties and Relaxor Behavior of a New (1-x)BaTiO₃–xBiAlO₃(1-x)BaTiO₃–xBiAlO₃ Solid Solution[J]. J. Appl. Phys., 2008, 103(3): 034114

[16] Luan W, Gao L, Guo J. Size Effect on Dielectric Properties of Fine-Grained BaTiO₃ Ceramics[J]. Ceram. Int., 1999, 25(8): 727-729.

[17] Fang C, Zhou D X, Gong S P. Core-Shell Structure and Size Effect in Barium Titanate Nanoparticle[J]. Physica B, 2011, 406(6): 1317-1322.

[18] Li H L, Kang J N, Guo F, et al. Effect of the Nb₂O₅ Content on Electrical Properties of Lead-Free BaTiO₃–Bi_0.5Na_0.5TiO₃ Ceramics[J]. Ceram. Int., 2013, 39: 7589-7593.

[19] Fang T T, Hsieh H L, Shiau F S. Effects of Pore Morphology and Grain Size on the Dielectric Properties and Tetragonal-Cubic Phase Transition of High-Purity Barium Titanate[J]. J. Am. Ceram. Soc., 1993, 76: 1205-1211.

[20] Evans R, Nowak U, Dorfbauer F, et al. The Influence of Shape and Structure on the Curie Temperature of Fe and Co Nanoparticles[J]. J. Appl. Phys., 2006, 99: 08G703.

[21] Wang Y, Miao K, Ma R. The Formation of Y5V-type Fine-Grained Ceramics Based on Spherical Submicron BaZr_0.1Ti_0.9O₃@Al₂O₃ Particles[J]. Ceram. Int., 2016, 42(13): 14627-14634.

[22] Maison W, Ananta S, Tunkasiri T, et al. Effect of Calcination Temperature on Phase Transformation and Particle size of Barium Titanate Fine Powders Synthesized by the Catecholate Process[J]. Science Asia, 2001, 27: 239-243.