Barium titanate thick films prepared by screen printing technique

The barium titanate (BaTiO3) thick films were prepared by screen printing technique using powders obtained by soft chemical route, modified Pechini process. Three different barium titanate powders were prepared: i) pure, ii) doped with lanthanum and iii) doped with antimony. Pastes for screen printing were prepared using previously obtained powders. The thick films were deposited onto Al2O3 substrates and fired at 850°C together with electrode material (silver/palladium) in the moving belt furnace in the air atmosphere. Measurements of thickness and roughness of barium titanate thick films were performed. The electrical properties of thick films such as dielectric constant, dielectric losses, Curie temperature, hysteresis loop were reported. The influence of different factors on electrical properties values was analyzed

PZT-NZF/CF ferrite flexible thick films: Structural, dielectric, ferroelectric, and magnetic characterization

The preparation and properties of thick flexible three-phase composite films based on lead zirconium titanate (PZT) and various ferrites (nickel zinc ferrite (NZF) and cobalt ferrite (CF)) were reported in this study. Properties of three-phase composite films were compared with pure polyvinylidene fluoride (PVDF) and PZT-PVDF films. X-ray diffraction data indicated the formation of well crystallized structure of PZT and NZF/CF phases, without the presence of undesirable phases. Scanning electron micrographs showed that the ceramic particles were dispersed homogeneously in the PVDF matrix and atomic force microscopy confirmed that the size of the particles is around 30 nm. Non-saturated hysteresis loops were evident in all samples due to the presence of highly conductive ferrite phases. Under magnetic field of 10 kOe, composite films exhibited a typical ferromagnetic response. Dielectric properties were investigated in the temperature range from -128 to 250 degrees C and frequency range of 400 Hz-1 MHz. The results showed that the value of dielectric constant of the PVDF/PZT/ferrite composites increased about 25% above the one obtained for pure PVDF

Magneto-dielectric properties of ferrites and ferrite/ferroelectric multiferroic composites

Ni-Zn ferrites, with the general formula Ni1-xZnxFe2O4 (x = 0.0, 0.3, 0.5, 0.7, 1.0), CoFe2O4, BaTiO3 and PbZr0.52Ti0.48O3 powders were synthesized by auto-combustion method. The composites were prepared by mixing the appropriate amounts of individual phases, pressing and conventional sintering. X-ray analysis, for individual phase and composites, indicated the formation of crystallized structure of NiZnFe2O4, BaTiO3 and PbZr0.52Ti0.48O3 without the presence of secondary phases or any impurities. SEM analyses indicated a formation of uniform grain distribution for ferromagnetic and ferroelectric phases and formation of two types of grains, polygonal and rounded, respectively. Magneto-dielectric effect was exhibited in all samples because of the applied stress occurring due to the piezomagnetic effect and the magnetic field induced the variation of the dielectric constant. For all samples the dielectric constant was higher in applied magnetic field. At the low frequency, the dispersion of dielectric losses appeared, while at the higher frequency the value of tan δ become constant (Maxwell-Wagner relaxation). Investigation of J-E relation between leakage and electric field revealed that both nickel zinc ferrite and composites have three different regions of conduction: region with ohmic conduction mechanism, region with the trap-controlled space charge limited current mechanism and region with space charge limited current mechanism

PZT-NICKEL FERRITE AND PZT-COBALT FERRITE COMPARATIVE STUDY: STRUCTURE, DIELECTRIC, FERROELECTRIC AND MAGNETIC PROPERTIES OF COMPOSITE CERAMICS

Multiferroic (MF) materials with simultaneous magnetic and electric long range order and occasionally, mutual magnetoelectric (ME) coupling, have recently attracted considerable interest. These compounds present opportunities for potential applications in information storage, the emerging field of spintronics, sensors, and multistate memory devices [1]. The ME phenomenon is observed in both single- phase as well as composite materials. The challenge in preparing such materials is to find equilibrium ferroelectric and magnetic structures preserving both properties close to the room temperature [2]. The individual phases (Ni0.7Zn0.3Fe2O4, CoFe2O4 and PbZr0.52Ti0.48O3) were prepared by citrate-nitrate combustion reaction method. Composites were prepared by mixing and homogenizing PZT and NZF/CF powders in a planetary ball mill in the ratio: (x) PZT + (1-x) CF/NZF (x = 0.8 and 0.9). XRD diagrams of a sintered composite confirm the presence of only two phases, ferroelectric PZT phase and ferrite phase. SEM analysis revealed a uniform grain arrangement of both phases. Similar values of saturation magnetization (Ms) for both types of composites were observed. Ms increases with increasing magnetic phase, as it was expected. Significantly higher values of coercive field (HC) can be seen in the composite with a cobalt-ferrite, which belongs to the group of hard ferrite unlike NZF which is soft ferrite and characterized by low values of coercive field. The ferroelectric properties of all ceramic composites were also studied

Characterization and properties of barium bismuth titanate

BaBi4Ti4O15 (BBiT) was prepared from stoichiometric amounts of BaTiO3 (BT) and Bi4Ti3O12 (BIT) obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. BBiTceramics were sintered at 1100°C, 1110°C and 1120°C for 1 h without pre-calcination step. The formation of phase and crystal structure of BT, BIT and BBiT were verified using X-ray analysis. The morphology of obtained powders and microstructure were examined using scanning electron microscopy. The electrical properties of sintered samples were carried out and BBiT shows behaviour typical for relaxor ferroelectrics and dielectric constant at room temperature is approximately 93

Effect of powder synthesis method on BaTiO3 ceramics

Barium titanate (BaTiO3) has been of practical interest for more than 60 years because of its attractive properties. BaTiO3 can be prepared using different methods, which can have significant influence on the structure and properties of barium titanate ceramics. In this paper powder of BaTiO3 powders were prepared by two methods. The first was synthesis from polymeric precursors through Pechini process which was carried out as a three-stage process from an oganometallic complex, producing cubic BaTiO3 powders with 40–80 nm primary particles. The second was a mechanochemical synthesis from powder mixture of BaO and TiO2, producing cubic BaTiO3 but with primary particles 200–250 nm. In both cases BaTiO3 ceramics were produced by sintering for 2h at 1300°C without a pre-calcination step. The phases formed and the crystal structure of BaTiO3 prepared by both methods was carried out by XRD analysis. The morphology and microstructure of obtained powders and sintered samples were examined by SEM

Dielectric, ferroelectric and magnetic properties of La doped Bi5Ti3FeO15 ceramics

Aurivillius Bi5Ti3FeO15 (BTF) and Bi5-xLax Ti3FeO15 (BLTF) ceramics were successfully synthesized by a simple solid state reaction method. The samples were characterized by X-ray diffraction with no impurity phase identified. SEM micrographs show an evident decrease of grain size of La modified ceramics in comparison with pure BTF. Dielectric properties were investigated in a wide range of temperatures (300-1000 K) and frequencies (1 Hz-1 MHz). The Curie temperature was found to decrease in BLTF when compared to BTF ceramics. An energy bandgap of 1.83 and 1.77 eV for the BTF and BLTF ceramics, respectively was determined from UV-Vis diffuse absorption spectrum. Influence of La doping on ferroelectric and ferromagnetic measurements of both samples was also performed. Very weak ferromagnetism inside BTF can be observed while samples with La content showed complete paramagnetic behavior

Infrared and Raman spectroscopy study of antimony doped barium titanate prepared from organometallic complex

Pure and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process, which was carried out as a three-stage process from organometallic complex. Obtained powder was pressed into pellets and sintering was performed at 1300 degrees C for 8 h with heating rate of 10 degrees C min(-1). The formation of phase and crystal structure of pure and Sb-doped barium titanate was approved by XRD analysis, Raman and IR spectroscopy. The influence of Sb doping on microstructure of barium titanate ceramics was investigated by scanning electron microscopy. Therefore, the relation between grain size, structure and properties of the obtained ceramics was analyzed. Influence of Sb doping on barium titanate properties was discussed

Influence of tungsten doping on dielectric, electrical and ferroelectric behavior of BaBi4Ti4O15 ceramics

The effect of tungsten (W6+) doping on modification of the structure, dielectric, ferroelectric and electrical properties of BaBi(4)Ti(4-x)WxO(15) (BBTWx, x = 0, 0.03, 0.05 and 0.07) was investigated. The ceramic samples were synthesized by the conventional solid state reaction method. XRD data indicated the formation of single-phase layered crystalline structure that confirmed orthorhombic structure type of all compositions with space group A2(1)am. SEM micrographs suggest that the grain size slightly decreases with W doping. The temperature dependent dielectric study revealed that the dielectric constant decreases with W doping while transition temperature slightly increases. Influence of tungsten on relaxor behavior and diffuseness of phase transition is also discussed. Effect of W doping on the dielectric and electrical properties were investigated in terms of ion doping and defect mechanism. The ferroelectric properties were studied by P-E hysteresis loop and it was observed that the remanent polarization increases with a small level of W doping

Magneto-electric properties of xNi(0.7)Zn(0.3)Fe(2)O(4) - (1-x)BaTiO3 multiferroic composites

Di-phase ceramic composites, with general formula xNi(0.7)Zn(0.3)Fe(2)O(4) - (1-x)BaTiO3(x = 0.9, 0.7, 0.5, 0.3, 0.1), were prepared by a mixing method. X-ray analysis, for powder and ceramics, indicated the formation of ferrite and barium titanate phases without the presence of the impurities. SEM analysis indicated that the composite morphology contained two types of grains, polygonal and rounded. Homogeneous microstructure and the smallest grain size were obtained in ceramics with 70% of barium titanate. The electrical properties of these materials were investigated using impedance spectroscopy, dielectric and ferroelectric measurements. The NZF-BT(30-70) composite has shown better electrical properties in comparison to other investigated ceramics, confirmed by dielectric and ferroelectric data analysis. Saturation magnetization and coercive field decreased with the increase of the content of ferroelectric phase