Far Infrared Reflection Spectra of Ba(Zn,Ta)O3-BaZrO3 Dielectric Resonator Material

The dielectric ceramic materiala Ba(Zn_1/3Ta_2/3)O₃–BaZrO₃ has extremely low dielectric loss at microwave frequencies. To investigate the lattice vibrations of Ba(Zn,Ta)O₃ and Ba(Zr, Zn, Ta)O₃ solid solutions, far infrared reflection spectra were measured from 50 to 4000 cm⁻¹ using a Fourier transform infrared spectrometer. These data were analyzed according to the classical dispersion theory. The spectra of Ba(Zn,Ta)O₃ are well fitted by using the 14 resonant modes, and the spectra of Ba(Zr, Zn, Ta)O₃ solid solution are fitted by assuming the normal distribution on resonant frequencies. The damping constant of these materials is discussed, and the values of tan δ calculated from the dispersion parameters agree with the measured values.     

Properties of Surface Barrier Layer Formed on a Semiconducting BaTiO3 Ceramic

A mechanism for formation of a capacitive layer is described. Copper was vacuum-evaporated onto the surface of a semiconducting BaTiO₃ ceramic, Ag paste was applied to this layer, and the capacitor was fired in air. A transition layer ∼3 μm thick was formed between the electrode and the n -type semiconducting ceramic; this layer exhibits characteristics typical of a p-n junction.     

Microwave Characteristics of (Zr, Sn)TiO4 and BaO-PbO-Nd2O3-TiO2 Dielectric Resonators

The microwave characteristics of two dielectric resonator materials were investigated. This research included (Zr, Sn)TiO₄, a material having the characteristics of a dielectric constant K = 38, Q = 7000 at 7 GHz, and temperature coefficient of resonant frequency τ _f, = 0 ppm/°C. The investigation determined the relations between the dielectric loss and micro-structures of this ceramic. Analysis by X-ray microanalyzer made it clear that the addition of Fe₂O₃ increased the dielectric loss of this ceramic because the Fe ions diffused into the grain. The other material investigated was BaO-PbO-Nd₂O₃-TiO₂, a ceramic having a dielectric constant of K = 88, Q = 5000 at 1 GHz, and τ _f= 0 ppm/°C. As this ceramic has a very high dielectric constant, it is useful for applications at frequencies <1 GHz.     

Preparation of ZnS and CdS fine particles with different particle sizes by a spray-pyrolysis method

In the preparation of ZnS and CdS fine particles by an ultrasonic spray-pyrolysis method, the particle size was changed from submicrometre to micrometre size by changing the concentration of the metal nitrates in the starting aqueous solution containing Zn(NO3)2 or Cd(NO3)2 and SC(NH2)2. The effects of temperature profile in the reactor furnace on the properties of prepared particles were also investigated by varying the temperature profiles: constant and increasing temperature distributions. The volume mean diameter of the prepared particles was found to be approximately proportional to the one-third power of the concentration of the metal nitrates in the solution. The crystalline phase and fluorescence properties of ZnS and CdS particles did not depend on the particle size. This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation of Submicrometer A12O3 Powder by Gas-Phase Oxidation of Tris (acetylacetonato) aluminum (111)

Fine A1₂O₃ powder was prepared by the gas-phase oxidation of aluminum acetyl-acetonate. The reaction products were amorphous material at 600° and 800°C, γ-Al₂O₃ at 1000° and 1200°C, and δ-Al₂O₃ at 1400°C. The powders consisted of spherical particles from 10 to 80 nm in diameter; particle size increased with increasing reaction temperature and concentration of chelate in the gas.