High-Temperature Dielectric Properties of Polycrystalline Ceramics

1988 ◽  
Vol 124 ◽  
Author(s):  
W. W. Ho
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Volume Expansion ◽  
Room Temperature ◽  
Experimental Methods ◽  
Dielectric Constants ◽  
Amorphous Phases ◽  
Temperature Loss ◽  
Polycrystalline Ceramics ◽  
Impurity Doping

ABSTRACTExperimental methods for determining the high-temperature millimeter-wave dielectric properties of solids are described and the data obtained on a wide variety of polycrystalline ceramics are reviewed. In general, the observed increase in dielectric constants with temperature can be modeled with a macroscopic dielectric virial expansion and shown to be primarily caused by an increase in polarizability due to volume expansion. The room-temperature loss tangents in low-absorption ceramics are probably caused by impurity doping of the primary and secondary crystalline phases at grain junctions and along grain boundaries. The rapid increase in loss tangent at high temperatures commonly observed in polycrystalline ceramics is associated with softening of intergranular amorphous phases resulting in an increase in localized electrical conductivity.

New Perovskite Nanomaterials and Their Integrations into High-k Dielectrics

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000072-000077
Author(s):  
Minoru Osada ◽  
Takayoshi Sasaki
Keyword(s):  
Dielectric Properties ◽  
Room Temperature ◽  
Bottom Electrode ◽  
Dielectric Constants ◽  
Dielectric Films ◽  
Layered Perovskite ◽  
Layer By Layer ◽  
High K ◽  
High K Dielectric ◽  
High Dielectric

We report on a bottom-up manufacturing for high-k dielectric films using a novel nanomaterial, namely, a perovskite nanosheet (LaNb2O7) derived from a layered perovskite by exfoliation. Solution-based layer-by-layer assembly of perovskite nanosheets is effective for room-temperature fabrication of high-k nanocapacitors, which are directly assembled on a SrRuO3 bottom electrode with an atomically sharp interface. These nanocapacitors exhibit high dielectric constants (k > 50) for thickness down to 5 nm while eliminating problems resulting from the size effect. We also investigate dielectric properties of perovskite nanosheets with different compositions (LaNb2O7, La0.95Eu0.05Nb2O7, and Eu0.56Ta2O7) in order to study the influence of A- and B-site modifications on dielectric properties.

Structural and dielectric properties of Bi2NbxVi−xO5.5 ceramics

1996 ◽  
Vol 11 (9) ◽  
pp. 2288-2292 ◽  
Author(s):  
K. B. R. Varma ◽  
K. V. R. Prasad
Keyword(s):  
Differential Scanning Calorimetry ◽  
Grain Size ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dielectric Constants ◽  
Scanning Calorimetry ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Bi2Nbx V1−xO5.5 ceramics with x ranging from 0.01 to 0.5 have been prepared. The crystal system transforms from an orthorhombic to tetragonal at x 3= 0.1 and it persists until x = 0.5. Scanning electron microscopic (SEM) investigations carried out on thermally etched Bi2NbxV1−xO5.5 ceramics confirm that the grain size decreases markedly (18 μm to 4 μm) with increasing x. The shift in the Curie temperature (725 K) toward lower temperatures, with increasing x, is established by Differential Scanning Calorimetry (DSC). The dielectric constants as well as the loss tangent (tan δ) decrease with increasing x at room temperature.

Dielectric Properties of β-SiAlON at High Temperature Using Perturbation Method

2008 ◽  
Vol 403 ◽  
pp. 121-123 ◽  
Author(s):  
Young Hoon Seong ◽  
Ha Neul Kim ◽  
Do Kyung Kim
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
Dielectric Properties ◽  
Perturbation Method ◽  
Hot Pressing ◽  
Room Temperature ◽  
Tangent Loss ◽  
Resonator Method

-SiAlON with various z-values (z = 0.5~4.0) were produced by hot pressing. The dielectric properties (dielectric constant and tangent loss) of -SiAlON were characterized by the post-resonator method at room temperature and by the perturbation method from room temperature to 1200 oC at 2.45 GHz, respectively. Effect of z-values and temperatures with -SiAlON were investigated.

Effect of Ti Content on Microstructure and Dielectric Properties of Li and Ti Co-Doped NiO Thin Films

2007 ◽  
Vol 336-338 ◽  
pp. 2639-2642 ◽  
Author(s):  
Ya Ru Zhang ◽  
Bo Ping Zhang ◽  
Yan Dong ◽  
Jing Feng Li
Keyword(s):  
Thin Films ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Dielectric Constants ◽  
Coating Method ◽  
Diffraction Peaks ◽  
Ti Content ◽  
Ti Doping ◽  
Co Doped

Li and Ti co-doped NiO thin films with 200 nm in thickness were deposited onto Pt/Ti/SiO2/ Si(100) substrates using a sol-gel spin-coating method. The effect of Ti doping content on microstructure and dielectric properties of Li0.10TixNi0.90-xO (x=5-20mol%) thin films was investigated. XRD results showed that all the Li0.10TixNi0.90-xO thin films consisted of a mixture of NiO, Li2NiO2 and NiTiO3 oxides. The intensities of the diffraction peaks for the NiTiO3 phase increased and those for NiO decreased with increasing Ti content, suggesting that a part of NiO phase combined with Ti to form NiTiO3 phase. The dielectric constants of all the Li0.10TixNi0.90-xO thin films at 102 Hz at room temperature ranged from 200 to 400 and increased with increasing Ti content. The frequency stability of the dielectric constant for the Li0.10TixNi0.90-xO thin films was also improved greatly with increasing Ti content.

Preparation and Dielectric Properties of Cu/PVDF Composite Films

2014 ◽  
Vol 1035 ◽  
pp. 417-421 ◽  
Author(s):  
Jian Wen Zhai ◽  
Ya Jun Wang ◽  
Jian Lou Deng ◽  
Chang Gen Feng
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Volume Fraction ◽  
Composite Films ◽  
Interfacial Polarization ◽  
Dielectric Constants ◽  
Pvdf Film ◽  
Continuous Increase ◽  
Better Than

nanoand micro size Cu were employed separately and investigated comparatively. Different volume fraction of Cu was added into PVDF film in order to investigate the content of filler effect on the dielectric properties of polymer composites. XRD and SEM were used to analyze the crystalline phase and microstructure of the films. The results show that two sizes of Cu have the same peak features, and with the continuous increase of the content of Cu, it disperse better in PVDF. The dielectric constant (ε) of the composite containing 16 vol% micro-CCTO filler is 16 at 100 Hz and room temperature, and its dielectric loss (tanδ) is only 0.15, which is substantially better than others. Besides, for 18 vol% nanoCu/PVDF composite tanδis 0.25 andεis 18 at 100 Hz. Moreover,εand tanδof nanoCu/PVDF composite are both higher than those of micro-Cu/PVDF. Analysis shows that the composites with nanoCu have higher dielectric constants, which is mainly from the interfacial polarization.

scholarly journals New superprotonic crystals with dynamically disordered hydrogen bonds: cation replacements as the alternative to temperature increase

2017 ◽  
Vol 73 (6) ◽  
pp. 1105-1113 ◽  
Author(s):  
Elena V. Selezneva ◽  
Irina P. Makarova ◽  
Inna A. Malyshkina ◽  
Nadezhda D. Gavrilova ◽  
Vadim V. Grebenev ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Hydrogen Bonds ◽  
Single Crystals ◽  
Diffraction Data ◽  
Room Temperature ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superprotonic Phase

Investigations of new single crystals grown in the K3H(SO4)2–(NH4)3H(SO4)2–H2O system from solutions with different K:NH4 concentration ratios have been carried out. Based on the X-ray diffraction data, the atomic structure of the crystals was determined at room temperature taking H atoms into account. It has been determined that [K0.43(NH4)0.57]3H(SO4)2 crystals are trigonal at ambient conditions such as the superprotonic phase of (NH4)3H(SO4)2 at high temperature. A distribution of the K and N atoms in the crystal was modelled on the basis of the refined occupancies of K/N positions. Studies of dielectric properties over the temperature range 223–353 K revealed high values of conductivity of the crystals comparable with the conductivity of known superprotonic compounds at high temperatures, and an anomaly corresponding to a transition to the phase with low conductivity upon cooling.

High Temperature Capacitors Based on [0001] and [1120] Sapphire Dielectrics

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000182-000187
Author(s):  
Liang-Yu Chen
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Dielectric Material ◽  
Dielectric Materials ◽  
Dielectric Constants ◽  
Polycrystalline Alumina ◽  
Temperature Range ◽  
Sapphire Substrates ◽  
Low Volume ◽  
Parallel Resistance

The test results of the dielectric properties of [0001] (C-plane) and [1120] (A-plane) sapphire (single crystalline Al2O3) at high temperatures indicate that these materials have very stable dielectric constants and low dielectric losses (compared with polycrystalline alumina) at low frequencies in the temperature range from room temperature to 550°C. Therefore, sapphire materials have become likely candidate dielectric materials for high temperature capacitors. This paper reports prototype low-volume (∼100pF) capacitors based on sapphire dielectrics for high temperature and low frequency applications. Low-volume parallel-plate capacitors using C-plane and A-plane sapphire as dielectric material were fabricated by stacking metallized sapphire substrates. These prototype capacitors were characterized in the temperature range from room temperature to 550°C by measuring the capacitance and parallel resistance of these devices at 120Hz, 1kHz, 10kHz, 100kHz, and 1MHz. The capacitance and equivalent parallel resistance of these capacitors were all directly measured by an AC LCZ impedance meter in controlled temperature environments. These prototype devices demonstrate stable capacitances over a wide temperature range, and therefore, have the potential to be integrated with silicon carbide (SiC) devices to enable high temperature electronics. The needs of thin-film metallization and encapsulation for these sapphire substrates are also discussed.

Thermoelectricity of Al-doped ZnO at different carrier concentrations

2007 ◽  
Vol 22 (7) ◽  
pp. 1942-1946 ◽  
Author(s):  
Yoshiaki Kinemuchi ◽  
Chihiro Ito ◽  
Hisashi Kaga ◽  
Tomohiro Aoki ◽  
Koji Watari
Keyword(s):  
High Temperature ◽  
Seebeck Coefficient ◽  
Carrier Concentration ◽  
Power Factor ◽  
Room Temperature ◽  
Boltzmann Constant ◽  
Zinc Oxides ◽  
Impurity Doping ◽  
Doped Zno ◽  
High Temperature Operation

Optimization of the carrier concentration is a key to improve the power factor of thermoelectricity. The carrier concentration of sintered zinc oxides was primarily controlled by impurity doping of aluminum and secondarily adjusted by defect concentration by varying the oxygen partial pressure in the range of 101 to 104 Pa. The resultant carrier concentration measured at room temperature ranged from 1 to 1.8 × 1020 cm−3, which drastically modified the thermoelectricity. The Jonker plot of the measured Seebeck coefficient and conductivity revealed deviation of the slope from k/e (where k is the Boltzmann constant and e is the elemental electric charge), which was attributed to a mobility variation with respect to the carrier concentration. The approach to estimating the optimum conductivity taking into account mobility variation is discussed. Finally, the optimum conductivity is estimated to be 1800 to 2000 S/cm for high-temperature operation (500 to 800 °C).

Microstructures and Dielectric Properties of CaCu3Ti4O12 Polycrystalline Ceramics

2007 ◽  
Vol 124-126 ◽  
pp. 143-146 ◽  
Author(s):  
Duk Keun Yoo ◽  
Sang Im Yoo
Keyword(s):  
Dielectric Properties ◽  
Sintered Density ◽  
Dielectric Constants ◽  
Abrupt Increase ◽  
Factors Affecting ◽  
Polycrystalline Ceramics ◽  
State Ceramic ◽  
Ceramic Process ◽  
Ccto Sample ◽  
Very High

We report important factors affecting the dielectric properties of CaCu3Ti4O12 (CCTO) polycrystalline ceramics prepared by the conventional solid-state ceramic process. The relative dielectric constants (εr) up to several thousands (~ 3,000 at 1 kHz) were gradually increased with increasing the sintered density of samples in the case that no exaggerated grain growth occurred. An abrupt increase in εr values were, however, accompanied by the formation of abnormally grown large grains, and thus with increasing the population of abnormally grown grains, which could be achieved by a prolonged sintering at 1060°C, the εr values were remarkably increased from several thousands to ~105. Optimally processed CCTO sample exhibited a very high εr of ~ 90,000 at 1 kHz.

scholarly journals Porous and Nonporous Film-Shaped Magnetorheological Nanocomposites: Dielectric and Electrical Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Aref Naimzad ◽  
Yousef Hojjat ◽  
Mojtaba Ghodsi
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Volume Resistivity ◽  
Comparative Investigation ◽  
Dielectric Constants ◽  
Dielectric Losses ◽  
Iron Particles ◽  
Electrical And Dielectric Properties

This paper presents a brief experimental comparative study on electrical and dielectric properties of two sets of porous and nonporous MRNCs, each including five samples of film-shaped magnetorheological nanocomposites (MRNCs) based on room temperature vulcanized (RTV) silicone rubber and nanosized carbonyl iron particles (CIPs). The electrical and dielectric properties of porous and nonporous MRNCs were measured at five different filler concentrations. Several experiments were performed to measure the volume resistivity, dielectric constant, and dielectric loss. The MRNCs dielectric properties were analysed with respect to the parameters like frequency and CIPs loadings. The electrical conductivity was studied in terms of volume resistivity. The comparative investigation suggests the porous MRNCs for smart and light-weighted structures those benefits from a lower electrical property, dielectric losses, and dielectric constants.

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