Donald L. Kinser

Effect of oxidizing and reducing atmospheres at elevated temperatures on the electrical properties of zinc oxide varistors

Voltage–current characteristics have been measured for varistors that have been heated in reducing or oxidizing gases. Reducing environments produced large decreases in the leakage resistance. However, the original varistor characteristics could be restored by subsequent heating in oxidizing ambients. The oxygen partial pressure below which degradation occurred is 100 Pa at 800 °C. Degradation by reducing ambients occurred at much lower temperatures (150–500 °C) than did restoration of the varistor characteristics by oxidizing ambients (500–700 °C). An explanation of the observed behavior is proposed.

Preparation effects on the UV optical properties of GeO2 glasses

The fusion temperature (Tφ), the oxygen partial pressure (PO2) during melting and the quenching rate from Tφ all influence the optical absorption in the 5.06‐eV (245‐nm) region. These observations are consistent with the assumption that the defect responsible for the optical absorption is an oxygen vacancy or complex of vacancies. The activation energy for the formation of the defect in GeO2 glasses which is repsonsible for the optical absorption is 2.3 eV which is larger than the activation energy for oxygen diffusion (∼1 eV).

Fabrication of Cu-coated Ag nanocrystals in silica by sequential ion implantation

Abstract Metal nanocrystal glass composites were fabricated by single and sequential element implantations of Ag + and Cu + ions into high purity silica. Implantation doses (×10 16 ions/cm 2 ) were 3Ag, 9Cu and 3Ag/9Cu. Composites were analyzed using Rutherford backscattering techniques (RBS), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and optical spectroscopy. An optical density spectrum based on the size distribution observed in the sequentially implanted sample for Cu shell and Ag core nanocrystals has been calculated using the dipole and quadrupole terms in a Mie series summation and is compared with the observed absorption spectrum. Results from TEM and EDS as well as the optical simulations demonstrate that Cu shell and Ag core nanocrystals are formed by the sequential implantation of Ag and Cu.

The influence of fusion temperature on the defect center concentration of GeO2 glass

Paramagnetic resonance spectra of virgin glasses and γ‐ray irradiated GeO2 glasses were studied with the electron spin resonance (ESR) method as a function of fusion temperatures. Fusions were made in air at temperatures between 1200 and 1650 °C and cooled at constant rate. In virgin glasses, only the E′ center was detected at concentrations of about 1015/g. After a γ‐ray irradiation, a new resonance at the low‐field side (lfs) of the E′1 center and a symmetric line with g=1.91 were observed. Measurements at various temperatures, power levels, and frequencies provide a basis for resolving the overlapping resonances. We labeled the paramagnetic center causing the lfs signal the H0 center. The g values of the H0 center are the basis for attributing this center to a hole located on a nonbridging oxygen. The g=1.91 resonance is attributed to Cr5+ or M5+0 impurities in the GeO2 glasses. At constant γ‐ray dose, the H0 center concentration decreased and the E1 ‐center concentrations increased with increase of fu...

Formation and optical properties of metal nanoclusters formed by sequential implantation of Cd and Ag in silica

Nanometer dimension metal colloids fabricated by sequential implantation of Cd then Ag in silica and by single element implantations of the same elements are characterized by transmission electron microscopy and optical spectroscopy. A nominal dose of 6 × 1016 ions/cm2 as determined by current integration was used for both ions species. The doses used for the sequential implantations were a 1 to 1 ratio of Cd to Ag. Sequential implantation of Cd and Ag leads to the formation of multi-component metal nanoclusters and elemental nanoclusters. The electron diffraction measurements were consistent with the formation of Ag5Cd8 and elemental Ag. With annealing the composition of the nanoclusters shifts to AgCd and elemental Cd. The optical responses are consistent with results expected from effective medium theory.

Effect of Melt Temperature on the dc Conductivity of GeO2 Glasses

The dc electrical properties of a series of high purity GeO2 glasses fused and equilibrated at various temperatures (Tφ) in air were measured. Tφ ranged from 1200 to 1690 °C. The observed changes are not correlated changes in concentration of any of the impurities as determined by neutron activation analyses or IR measurements of OH concentrations. The resistivity was found to obey an Arrhenius function with enthalpy of activation of approximately 1.0 eV for all Tφ’s except for Tφ =1200 °C. The charge carrier was concluded to be the Na+ ion. The mobility of the Na+ ion was calculated and was found to be a function of Tφ. We suggest that the change in Tφ results in a change in the configuration coordinates of the average interstitial sites through which the Na+ ion moves. This change results in differences in the vibrational energy structure of the interstitial sites. These differences are manifested in the entropy of activation. With changes in the entropy of activation, the preexponential term changes, p...

Charge trapping and release in electron and gamma irradiated lead silicate glasses

Abstract The thermally stimulated release of charge in electrically polarized and electron and gamma irradiated glasses containing 30 to 50 mol% PbO was investigated between 290 and 450 K. The release of trapped change in irradiated glasses produced a thermally stimulated current peak which had the same activation energy as the depolarization current peak in electrically polarized specimens. The irradiation induced dielectric breakdown of these glasses was correlated with the quantity of trapped charge and the relaxation time for charge release determined from the thermally stimulated depolarization current.

Optical phenomena observed in low‐energy ion and electron bombardment of silica surfaces

Optical spectroscopy has been used to characterize the interaction of ionizing radiation with glasses, including ions with energies in the 3–10 keV range, and electrons with energies ranging from 320 to 640 eV. Characteristic line emission spectra of desorbed excited atoms, as well as luminescence spectra from the near‐surface bulk, were observed. A search for possible changes in desorption mechanisms as a function of radiation dose was carried out by observing the time dependence of integrated intensity and spectral linewidth for desorbed silicon and the trace element calcium. Defect formation in the near‐surface bulk was monitored by spectrally resolved, time‐dependent measurements of the bulk luminescence and by electron paramagnetic resonance spectroscopy. These spectroscopic observations are correlated with identifiable differences in the manufacturing processes of several silicas, and thus can be related to one particular kind of surface radiation damage, namely, ion‐ and electron‐induced desorption.

Electrical properties of praseodymium phosphate glasses

Abstract The electrical properties of PrO x P 2 O 5 glasses with constant P 2 O 5 have been examined as a function of oxidation and reduction treatments. The electrical conductivity of this 4f series glass is markedly lower in magnitude from the 3d, 4d, and 5d transition metal glasses, but the Mott formalism successfully rationalizes the properties. The glass forming range is limited to approximately 40 mol% PrO x .

AG:CD and CD:AG implantations into high purity silica

Abstract Silica composites containing nanometer dimension colloids were fabricated by implantation of Ag ions followed by Cd ions, and by implantation of Cd ions followed by Ag ions. These samples were characterized using transmission electron microscopy and optical spectroscopy. Doses used for the sequential implantations were 6×1016 ions/cm2 of Ag and Cd in a 1 to 1 ratio. Single element colloids were also fabricated by implantation of Ag or Cd using the same nominal dose and implantation energy as the sequential implantations. Sequential implantation of Ag and Cd leads to the formation of multi-component metal nanoclusters and elemental nanoclusters. Different microstructures were obtained depending on the order of implantation. Optical responses are consistent with results expected from effective medium theory.