Relationship between structural and dielectric properties of Zn-substituted Ba5CaTi2−xZnxNb8O30 tetragonal tungsten bronze (original) (raw)
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Materials Sciences and Applications, 2018
Tungsten bronze structure ceramics have found vital potential in many applications such as actuators, transducer, electro-optic, ferroelectric random access memory and microwave devices. These type ceramics are extensively used in many industrial applications due to their spontaneous polarization and well-known for its high dielectric constant, low dielectric loss, low leakage current density, good thermal stability and high piezoelectric coefficient. In present work, Ba5CaTi2Nb8O30 (BCTN) has been synthesized first time through solid state reaction method. The microstructures, dielectric, ferroelectric, ferromagnetic and Raman spectra have been investigated by means of X-ray diffraction, Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), LCR meter, P-E loop tracer, VSM and Raman spectrometer respectively. X-ray dif-fraction study revealed the formation of single phase tetragonal structure with space group P4bm. The crystallite size was observed to be in th...
Dielectric response of tungsten modified Ba(Ti0.90Zr0.10)3 ceramics obtained by mixed oxide method
Processing and Application of Ceramics, 2010
The electrical response of Ba(Ti0.90Zr0.10)O3 (BZT) ceramics obtained by the mixed oxide method as a function of tungsten content was investigated. According to X-ray diffraction analysis the single phase BZT1W (1 wt.% W doped BZT) and BZT2W (2 wt.% W doped BZT) ceramics, crystallized in a perovskite structure, were obtained. It is also shown that tungsten substituted ceramics can be sintered at a reduced temperature when compared to the undoped BZT. Electron paramagnetic resonance (EPR) analyses reveals that substitution of Ti4+ by W6+ causes distortion in the crystal structure changing lattice parameter. Substitution of W6+ on B-site of ABO3 perovskite BZT ceramics shifted the phase transition to lower temperatures up to a tungsten content of 2 wt.% leading to a relaxor-like behaviour.
Journal of Alloys and Compounds, 2017
The polycrystalline samples of the new ferroelectric ceramics ሺ1 − ݎܵሻݔ ଷ.ଷହ ܽܤ ଵ.ହ ܾܰ ଵ ܱ ଷ (SBN)-ሺݔሻܽܤ ସ ܰܽ ଶ ܾܰ ଵ ܱ ଷ (BNN) with potassium tungsten bronze structure were prepared using a high-temperature solid-state reaction technique. They are novel inorganic materials with potassium tungsten bronze structural type. The formation of the ceramics under the reported conditions has been confirmed by an X-ray diffraction technique. The ceramic microstructures were observed using scanning electron microscopy (SEM) techniques associated with energy dispersive X-ray spectroscopy (EDX) analysis. The SEM micrograph exhibits grain boundary distribution. Dielectric properties of the SBN-NBN compounds as a function of temperature (300-850 K) at frequencies 1-1000 KHz were studied. Detailed studies of variation of dielectric parameters with temperature and frequency confirmed the existence of ferroelectricity in these materials. The difference between the highfrequency dielectric constants and the low-frequency dielectric constants indicates that the ferroelectric phase transition in SBN-NBN compounds is of rather diffuse nature than relaxor type. According to the experimental data, it is suggested that ferroelectrics phase transition is a first-order transition.
Processing and Application of Ceramics
In this work, the effects of Ba(Fe0.5Nb0.5)O3 (BFN) addition on the structure and dielectric behaviour of Ba0.06(Na0.5Bi0.5)0.94TiO3 (BNBT) ceramics have been reported. The lead-free (1-x)BNBT-xBFN (where 0 ? x ? 1.0) solid-solutions were synthesized by traditional ceramics fabrication technique and sintered at temperatures up to 1325?C. The X-ray diffraction peaks of the compounds of the entire series were indexed. It is found that the crystal structure of the obtained solid solutions changed from rhombohedral (R3c) to cubic (Pm3m) with an increase in BFN content. The Fourier transformed infrared and Raman spectra also confirmed the formation of solid-solutions. SEMstudies were carried out to evaluate the purity and microstructure of the fabricated ceramics. The dependence of phase transition broadening, phase transition temperature and dielectric parameters with compositional changes were also studied.
Journal of the American Ceramic Society, 2006
BaCu(B 2 O 5) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B 2 O 5) phase was formed at 7001C and melted above 8501C. The BaCu(B 2 O 5) ceramic sintered at 8101C had a dielectric constant (e r) of 7.4, a quality factor (Q Â f) of 50 000 GHz and a temperature coefficient of resonance frequency (s f) of À32 ppm/1C. As the BaCu(B 2 O 5) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B 2 O 5) was added to the Ba(Zn 1/3 Nb 2/3)O 3 (BZN) ceramic, BZN ceramics were well sintered even at 8501C. BaCu(B 2 O 5) existed as a liquid phase during the sintering and assisted the densification of the BZN ceramic. Good microwave dielectric properties of Q Â f 5 16 000 GHz, e r 5 35, and s f 5 22.1 ppm/1C were obtained for the BZN16.0 mol% BaCu(B 2 O 5) ceramic sintered at 8751C for 2 h.
Structure and Dielectric Properties of Lead-Free BaSn 0.1 Ti 0.9 O 3 -BaFe 0.5 Nb 0.5 O 3 Ceramics
Ferroelectrics, 2014
Lead free piezoelectric ceramics (1 À x)BNLT ÀxBZT with x ¼ 0.00, 0.06, 0.09 and 0.12 were prepared using a two-step mixed oxide method. Dielectric, ferroelectric and piezoelectric properties of the ceramics were improved by the addition of the BZT. XRD results show tetragonal symmetry structure of the BNLT-BZT ceramics. It was found that the tetragonality increases with increasing BZT content. The optimum composition is x ¼0.09, where the maximum values of the piezoelectric constant d 33 ( 126pC/N)anddielectricconstant(126 pC/N) and dielectric constant ( 126pC/N)anddielectricconstant(2400) were obtained at room temperature. This BNLT-BZT system can be a promising candidate for lead-free piezoelectric ceramics.
Ba(Ti 1?x Sn x )O 3 (x=0.13) Dielectric Ceramics Prepared by Coprecipitation
Journal of the American Ceramic Society, 2007
Fine-grain BaTi 0.87 Sn 0.13 O 3 (BTS 13 ) powder was synthesized from an oxalate precursor and used to prepare sintered ferroelectric BTS 13 ceramics. The evolution of the morphology and structure of a BTS 13 precipitate precursor as a function of temperature was analyzed. We compare the sintering behavior as well as the dielectric properties of the BTS 13 ceramics obtained using uniaxial and cold isostatic pressing.