Investigation of Sr1-xCaxTiO3 ceramics dedicated to high-frequency lead-free components

2018 ◽  
Vol 11 (05) ◽  
pp. 1850005 ◽  
Author(s):  
H. Ait Laasri ◽  
D. Fasquelle ◽  
A. Tachafine ◽  
N. Tentillier ◽  
L. C. Costa ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Frequency ◽  
Room Temperature ◽  
Lead Free ◽  
Dielectric Measurements ◽  
Solid State Reaction Technique ◽  
Phase Purity ◽  
Wide Range ◽  
Temperature Ranges ◽  
Extended Frequency

Lead–free Sr[Formula: see text]CaxTiO3 ([Formula: see text]) ceramics were synthesized via a solid state reaction technique at room temperature. The effects of ionic substitutions in A-sites between strontium and calcium on the structural and dielectric properties were investigated. XRD technique was used to identify the crystal structure and to demonstrate the phase purity. SEM observations have shown homogeneous morphologies for all samples. Dielectric measurements were investigated for a wide range of frequency (100[Formula: see text]Hz–1[Formula: see text]GHz) and temperature (25[Formula: see text]C–250[Formula: see text]C). Strontium substitution by calcium has not only led to a decrease in the dielectric permittivity value, but also to the loss tangent value by a considerable factor. Interesting values of the quality factor and the quite constant value [Formula: see text] in extended frequency and temperature ranges show that SCT ceramic could be a real candidate for the development of monolithic ceramic capacitors dedicated to high-frequency lead-free components and/or to extremely high-temperature environments.

Piezoelectric properties of lead-free (Na0.5Bi0.5)TiO3–(Na0.5K0.5)NbO3–BaTiO3 ceramics

2008 ◽  
Vol 23 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Seung-Ho Lee ◽  
Chang-Bun Yoon ◽  
Sung-Mi Lee ◽  
Hyoun-Ee Kim ◽  
Kyung-Woo Lee
Keyword(s):  
Crystal Structure ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Microstructural Evolution ◽  
Piezoelectric Properties ◽  
Lead Free ◽  
Cubic Phase ◽  
Lead Free Ceramics ◽  
Wide Range

The microstructural evolution and piezoelectric properties of lead-free ceramics (0.98-x)(Na0.5Bi0.5)TiO3–x(Na0.5K0.5)NbO3–0.02BaTiO3 (0 ⩽ x ⩽ 0.98, abbreviated as (0.98-x)NBT–xNKN–0.02BT) were investigated. The effects of the amount of NKN on the crystal structure, microstructural evolution, and piezoelectric properties were examined. The 0.93NBT–0.05NKN–0.02BT ceramics having a lower NKN content gave good performances with piezoelectric properties of d33 = 140 pC/N and kp = 21%, because of the soft additive Nb5+ ions at the B sites. However, a paraelectric cubic phase was observed in the wide range of compositions between x = 0.1 and x = 0.9. At a higher NKN content of x > 0.9, a morphotropic phase boundary (MPB) between the tetragonal and orthorhombic phases was found in the 0.015NBT–0.965NKN–0.02BT ceramics, and the piezoelectric properties were enhanced (d33 = 135 pC/N, kp = 29%). The piezoelectric properties of this system were closely related to its crystal structure.

Dielectric and Piezoelectric Properties of (Na,Ba)(Nb,Ti)O3 Lead-Free Piezoelectric Ceramics

2010 ◽  
Vol 445 ◽  
pp. 55-58 ◽  
Author(s):  
Rintaro Aoyagi ◽  
Makoto Iwata ◽  
Masaki Maeda
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Electromechanical Coupling ◽  
Piezoelectric Properties ◽  
Electromechanical Coupling Factor ◽  
Coupling Factor ◽  
Lead Free ◽  
Dielectric And Piezoelectric Properties

(Na1-xBax)(Nb1-xTix)O3 (NNBTx; x=0.0-0.21) solid-solution ceramics were synthesized and their crystal structure, dielectric properties and piezoelectric properties were investigated. The crystal structure at room temperature of NNBTx varied from orthorhombic to tetragonal with increasing BaTiO3 content x. The phase boundary between orthorhombic and tetragonal at room temperature was confirmed BT content between x=0.08 and 0.09. For x>0.05, it was found that the Curie temperature was decreased with increasing x. The highest electromechanical coupling factor, kp, and the largest piezoelectric constant, d33, were obtained at x=0.09-0.10.

Processing and Characterization of (1-x)(Na1/2Bi1/2)TiO3 - xLa(Mg1/2Ti1/2)O3 Ceramics

2006 ◽  
Vol 514-516 ◽  
pp. 250-254 ◽  
Author(s):  
Andrei N. Salak ◽  
Nikolai P. Vyshatko ◽  
Andréi L. Kholkin ◽  
Victor M. Ferreira ◽  
Nikolay M. Olekhnovich ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Bismuth Titanate ◽  
Lead Free ◽  
Dielectric Characteristics ◽  
Compositional Evolution ◽  
Evolution Of Structure ◽  
Permittivity Maximum

Lead-free relaxor ceramics based on sodium-bismuth titanate, (1-x)(Na1/2Bi1/2)TiO3 - xLa(Mg1/2Ti1/2)O3 [(1-x)NBT-xLMT] (0≤x≤0.25), were prepared by both the conventional mixed oxide method and by the Pechini route, and their crystal structure and dielectric properties were investigated. All the compositions studied were found to possess a rhombohedrally distorted crystal lattice at room temperature. A distortion degree of the unit cell decreases and its volume increases with LMT content. The temperature of the dielectric permittivity maximum does not change with increasing substitution rate. As x is increased, the frequency-dependent dielectric peaks are flattened. The compositional evolution of structure and dielectric characteristics of the ceramics obtained are analysed and discussed in respect to size, charge and polarizability of the cations involved.

Varistor Beahavior in Lead Based Perovskite Comounds

2001 ◽  
Vol 685 ◽  
Author(s):  
Seema Sharma ◽  
R.N.P. Choudhary
Keyword(s):  
Room Temperature ◽  
X Ray Diffraction ◽  
Solid State Reaction Technique ◽  
X Ray ◽  
Current Voltage ◽  
Wide Range ◽  
Ptcr Effect ◽  
Different Temperatures ◽  
Structure And Microstructure ◽  
Scanning Electron

Polycrystalline samples of Pb(Cd1/2W1/2)O3 and Pb(Mo1/2W1/2)O3 were synthesized by a high-temperature solid-state reaction technique. Preliminary crystal structure and microstructure of the compounds at room temperature were studied using X-ray diffraction (XRD) technique and Scanning electron microscopy (SEM), respectively. The dielectric permittivity (⊏) and losstangent (tan ⊏) of the compounds were obtained both as a function of frequency(103-104Hz) atroom temperature and temperature (30-3200C) at 10 kHz. Both the ac and dc conductivity have been studied over a wide range of temperature. The current– voltage (I-V) characteristics of the compound studied at different temperatures reveal that the Pb(Cd1/2W1/2)O3 also has excellent varistor behavior. A PTCR effect and NTCR effect was exhibited by Pb(Cd1/2W1/2)O3 and Pb(Cd1/2Mo1/2)O3 respectively.

Electrical and Magnetic Properties of Mg-Cr and Co-Cr Nano Ferrites Synthesized by Citrate-Gel Method

2015 ◽  
Vol 241 ◽  
pp. 69-92 ◽  
Author(s):  
M. Raghasudha ◽  
D. Ravinder ◽  
P. Veerasomaiah
Keyword(s):  
Electron Microscopy ◽  
Magnetic Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
High Frequency ◽  
Room Temperature ◽  
Hysteresis Loops ◽  
Dielectric Measurements ◽  
Electrical And Magnetic Properties ◽  
Potential Applications

The work deals with the study of electrical and magnetic properties of Magnesium-Chromium and Cobalt-Chromium nanoFerrites for their potential applications synthesized by Citrate-Gel auto-combustion method. Structural Characterization of prepared nanoferrites was performed using XRD, SEM, EDS and TEM. XRD patterns confirmed the formation of homogeneous single phased cubic spinel belonging to the space group Fd3m (in agreement with ICSD Ref. data). It is found that crystallite size of Mg-Cr ferrites was in the range of 7-23nm and that of Co-Cr nanoferrites in the range of 6-12 nm. Structural morphology of both the ferrites was studied by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). Elemental compositional analysis was carried out by EDS.Electrical properties such as D.C. resistivity of prepared Mg-Cr and Co-Cr nanoferrites were studied by two probe method. The dielectric measurements as a function of frequency at room temperature were performed in the frequency range of 20Hz to 2MHz using LCR meter. Various dielectric parameters like dielectric constant (ε′), dielectric loss (ε′′) and dielectric loss tangent (tan δ) were measured as a function of frequency. The magnetization measurements of the prepared nanoferrite samples were carried out at room temperature in the applied field of ±15KOe using Vibrating Sample Magnetometer (VSM). From the obtained M-H loops, various magnetic parameters such as Saturation Magnetization (Ms), Coercivity (Hc) and Remanence Magnetization (Mr) were measured. Magnetization as a function of field (±10T) at 5K, 25K, 300K temperatures was measured using VSM. Super-paramagnetic nature of some specified samples in Mg-Cr nanoferrites system was investigated from the temperature dependence of both the field cooled (FC) and the zero-field cooled (ZFC) magnetization measurements under a field of 100 Oe in the temperature range 5K to 350K.From the results of D.C. resistivity measurements it is observed that the resistivity decreases with increase in temperature for both Mg-Cr and Co-Cr nanoferrites suggesting the semiconducting behavior of the samples. Dielectric measurements suggest that the conduction in the ferrite systems may be due to the polaron hopping mechanism. The low loss tangent values at high frequency show the potential applications of these materials in high frequency microwave devices. Mg-Cr nanoferrites were synthesized yielding narrow hysteresis loops which are the characteristic of very soft magnetic materials that are desirable for their utility in Transformers, Inductor cores, Microwave devices and Magnetic shielding. Hysteresis loops of Co-Cr nanoferrites show the medium hard magnetic behavior of the materials. MgFe2O4 shows superparamagnetic behavior above room temperature and MgCr0.9Fe1.1O4 shows superparamagnetic behavior with the blocking temperature 94.5K. Hence these nanoferrites find applications in targeted drug delivery and in Magnetic Resonance Imaging (MRI) in biomedical field. The observed results can be explained in detail on the basis of composition and crystallite size.Contents of Paper

Evaluating the polymorphic phase transition in calcium-doped Ba(Zr0.05Ti0.95)O3: a lead-free piezoelectric ceramic

2013 ◽  
Vol 46 (2) ◽  
pp. 324-331 ◽  
Author(s):  
Gurvinderjit Singh ◽  
V. S. Tiwari ◽  
P. K. Gupta
Keyword(s):  
Room Temperature ◽  
Composition Range ◽  
Piezoelectric Properties ◽  
Ferroelectric Ceramic ◽  
Lead Free ◽  
Dielectric Measurements ◽  
Polymorphic Phase Transition ◽  
Tetragonal Crystal ◽  
Tetragonal Crystal Structure ◽  
Dielectric And Piezoelectric Properties

Structural and dielectric investigations were carried out on a perovskite lead-free (Ba1−xCax)(Zr0.05Ti0.95)O3ferroelectric ceramic forx= 0.03, 0.05, 0.08, 0.10, 0.12 and 0.15. The room-temperature structural analysis reveals a crossover from orthorhombic to tetragonal crystal structure nearx= 0.10. A coexistence of tetragonal (P4mm) and orthorhombic (Pmm2) structure is observed in the composition range 0.05 ≤x≤ 0.10. The fraction of tetragonal phase increases from 27% forx= 0.05 to 71% forx= 0.10. The dielectric measurements show that the tetragonal to orthorhombic and rhombohedral to orthorhombic transition temperatures decrease with an increase in Ca2+content, while the cubic to tetragonal transition temperature remains the same. It is also shown that for the tetragonal to orthorhombic transition a phase coexistence occurs over a temperature range of about 18 K. The coexistence range covers room temperature for intermediate compositions:x= 0.05, 0.08 and 0.10. Therefore, higher dielectric and piezoelectric properties are observed in these compositions.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Evaluation of 99mTc-Label led Vitamin K4 as an Agent for Testicular Imaging

1991 ◽  
Vol 30 (01) ◽  
pp. 35-39 ◽  
Author(s):  
H. S. Durak ◽  
M. Kitapgi ◽  
B. E. Caner ◽  
R. Senekowitsch ◽  
M. T. Ercan
Keyword(s):  
Soft Tissue ◽  
Room Temperature ◽  
Normal Subjects ◽  
Left Testis ◽  
Wide Range ◽  
Activity Ratios ◽  
The Right ◽  
Radioactivity Levels

Vitamin K4 was labelled with 99mTc with an efficiency higher than 97%. The compound was stable up to 24 h at room temperature, and its biodistribution in NMRI mice indicated its in vivo stability. Blood radioactivity levels were high over a wide range. 10% of the injected activity remained in blood after 24 h. Excretion was mostly via kidneys. Only the liver and kidneys concentrated appreciable amounts of radioactivity. Testis/soft tissue ratios were 1.4 and 1.57 at 6 and 24 h, respectively. Testis/blood ratios were lower than 1. In vitro studies with mouse blood indicated that 33.9 ±9.6% of the radioactivity was associated with RBCs; it was washed out almost completely with saline. Protein binding was 28.7 ±6.3% as determined by TCA precipitation. Blood clearance of 99mTc-l<4 in normal subjects showed a slow decrease of radioactivity, reaching a plateau after 16 h at 20% of the injected activity. In scintigraphic images in men the testes could be well visualized. The right/left testis ratio was 1.08 ±0.13. Testis/soft tissue and testis/blood activity ratios were highest at 3 h. These ratios were higher than those obtained with pertechnetate at 20 min post injection.99mTc-l<4 appears to be a promising radiopharmaceutical for the scintigraphic visualization of testes.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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