Quantization of the radiation field in an anisotropic dielectric medium

There are both loss and dispersion characteristics for most dielectric media. In quantum theory the loss in medium is generally described by Langevin force in the Langevin noise （LN） scheme by which the quantization of the radiation field in various homogeneous absorbing dielectrics can be successfully actualized. However, it is invalid for the anisotropic dispersion medium. This paper extends the LN theory to an anisotropic dispersion medium and presented the quantization of the radiation field as well as the transformation relation between the homogeneous and anisotropic dispersion media.

High permittivity of Ba(Ti_(1-x)Zr_(x))O_(3)-based Y5V-type nanopowders and ceramics synthesized using a one-step sol-gel method

We synthesized Ba(Ti_(1-x)Zr_(x))O_(3)-based(BTZ)nanopowders modified with Cu and Nb,and sintered ceramics using a one-step sol-gel process.Characterization using TG-DTG,XRD,SEM,and TEM analysis methods revealed that the powders formed at a nanometer scale.The process was controlled by the composition and calcining temperature.BaZrO3 formed earlier than BaTiO3 during the calcining,then a Ba(Ti_(1-x)Zr_(x))O_(3) solid solution formed incompletely,resulting in ceramics with huge permittivity and good temperature stability.Moreover,the maximum dielectric constant(εmax)first increased and then decreased as the Curie temperature(Tc)shifted to a lower temperature.When the Zr concentration was 5.4 mol%,εmax was greater than 24,000 and the dielectric loss(25℃)was only 0.005;this meets the Electronic Industries Alliance Y5V specifications.These nanopowders would permit a significant reduction in the thickness of multilayer ceramic capacitors and the huge pemittivity of the ceramics will help meet the current demand for device miniaturization in the electronics industry.

Synthesis and characterization of lead-free ternary component BST-BCT-BZT ceramic capacitors

Polycrystalline sample of lead-free 1/3(Ba_(0.70)Sr_(0.30)TiO_(3))+1/3(Ba_(0.70)Ca_(0.30)TiO_(3))+1/3(BaZr_(0.20)Ti_(0.80)O_(3))(BST-BCT-BZT)ceramic was synthesized by solid state reaction method.Phase purity and crystal structure of as-synthesized materials was confirmed by X-ray diffraction(XRD).Temperature-dependent dielectric permittivity studies demonstrated frequency independent behavior,indicating that the studied sample has typical diffuse phase transition behavior with partial thermal hysteresis.A ferroelectric phase transition between cubic and tetragonal phase was noticed near room temperature(~330 K).Bulk P-E hysteresis loop showed a saturation polarization of 20.4μC/cm^(2) and a coercive field of~12.78 kV/cm at a maximum electric field of~115 kV/cm.High dielectric constant(ε~5773),low dielectric loss(tanδ~0.03)were recorded at room temperature.Discharge energy density of 0.44 J/cm^(3) and charge energy density of 1.40 J/cm^(3) were calculated from nonlinear ferroeletric hysteresis loop at maximum electric field.Dielectric constant at variable temperatures and electric fields,ferroeletric to paraelectric phase transition and energy storage properties were thoroughly discussed.

Giant permittivity and good thermal stability of LiCuNb_(3)O_(9)-Bi(Mg_(0.5)Zr_(0.5))O_(3) solid solutions

(1-x)LiCuNb_(3)O_(9)-Bi(Mg_(0.5)Zr_(0.5))O_(3) ceramics((1-x)LCN-xBMZ)with 0≤x≤0.08 were synthesized by a solid-state reaction method.The phase structure of(1-x)LCN-xBMZ ceramics was characterized by X ray diffraction(XRD),which revealed that the ceranics were distorted cubic perovskite structures.Apparent giant permitivity of 1.98× 10^(4)-1.05× 10^(5) at 100kHz over the measured temperature range(259℃-250℃)was observed in the sintered(1-x)LCN-xBMZ(0≤x≤0.08)ceramics.Especially for the sample of x=0.04,the temperature stability of permitivity was markedly increased(△ε/ε100℃≤±15%),and high relative permitivity(>8.3 × 10^(4))were obtained over a wide temperature range from 100℃ to 250℃at 100 kHz,which indicates that this ceramic is a promising dielectrice material for elevated temperature dielectrics.The giant dielectric property of(1-x)LCN-xBMZ ceramics are profoundly concerned with the Maxwell-Wagner effect.