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Synthesis of Sr‐ and Ba titanate particles coated on Al 2 O 3 substrates forming a core‐shell structure
Author(s) -
Lehmann Sebastian,
Bauer Johann,
Ensinger Wolfgang
Publication year - 2020
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13511
Subject(s) - materials science , scanning electron microscope , x ray photoelectron spectroscopy , titanate , calcination , transmission electron microscopy , analytical chemistry (journal) , doping , chemical engineering , composite material , mineralogy , ceramic , nanotechnology , biochemistry , chemistry , optoelectronics , chromatography , engineering , catalysis
Abstract Sr‐ and Ba titanate particles doped with Nb, Mn, and Ce were produced via a wet‐chemical precipitation process based on salt solutions and metal chlorides around Al 2 O 3 flake‐like particles. In a calcination process at high temperatures, a shell of doped oxides is formed that is responsible for the unusual electrical properties. The particles were investigated via scanning electron microscope (SEM) and transmission electron microscope which showed homogeneously covered Al 2 O 3 particles. X‐ray diffraction exposed secondary phases besides BaTiO 3 and SrTiO 3 because of the high solubility of Ba(OH) 2 and Sr(OH) 2 in water and a resulting shortfall of earth alkaline metal. The oxidation states of the doping elements were determined via X‐ray photoelectron spectroscopy. Composite materials prepared from this filler and silicone rubber showed typical nonlinear voltage‐current (U‐I) characteristics, which are of special interest for high voltage engineering. The filler was evenly distributed within the matrix without settling while cross‐linking of the polymer, which was shown in an SEM‐backscattered electron image. The nonlinearity coefficient α , which is an important factor for field grading applications, was determined for different materials and reached a value of up to 7.