Yoshiaki Taketa

Oscillation phenomenon in ThO2‐doped SnO2 exposed to CO gas

In the ThO2‐doped SnO2 a new self‐oscillation phenomenon has been found only when it is exposed to CO gas. This phenomenon is related to the environmental CO gas concentration, substrate temperature, and applied voltage. The oscillation is extremely senstivie to the concentration of CO gas, especially in the region of 0.2‐0.3%.

Electrical conduction in thick film resistors

The formation and electrical properties of the conductive network in RuO2 thick film resistors were investigated. As a result, a RuO2 thick film resistor having a high concentration of RuO2 has conductive chains of RuO2 and metal-like conduction. However, the resistor having a low RuO2 concentration has a reactive Layer that allows it to maintain its conductivity even though there are no conductive paths by mutual contact of RuO2 particles; it also has amorphous, semiconductor-like characteristics.

Control of Electrical Properties of RuO2 Thick Film Resistors

Oxides of various elements have been added to RuO2 thick film resistors and the electrical properties of the resultant resistors have been examined.

New oscillation phenomena in VO2 crystals

New oscillation phenomena in VO2 crystals were observed. The oscillation is generated in the temperature region of the crystal transition, and its voltage and frequency depend upon the ambient temperature. The waveform of the oscillation is a rectangular pulse.

Thick Film Resistors with Improved Voltage Stability

Thick film resistors have been prepared by adding glass frits to the conductive materials of the resistors. By this method, it is found that the resistance of the glass phases in the thick film resistors decreases, with a resulting decrease of voltage drift after applying high voltage pulses to the resistors. In addition, the electrical properties and stability of these resistors are improved over resistors made from some present commercially available pastes.

The Effect of Various Factors on the Resistance and TCR of RuO2 Thick Film Resistors—Relation Between the Electrical Properties and Particle Size of Constituents, the Physical Properties of Glass and Firing Temperature

Thick film resistors were prepared with different variables, they included various conductive particle sizes, glass particle sizes, glass softening temperatures, thermal expansion coefficients of the glass, mixing ratios of the conductive element and glass, firing temperatures, firing cycles, etc. The relation between these factors and electrical properties of the thick film resistors was studied. As a result, it was found that when a specific glass is chosen, its R-TCR curve, which indicates the relation between resistance and TCR of a thick film resistor, is unconditionally fixed regardless of various preparation factors, and the R-TCR curve can be moved only by changing the thermal expansion coefficient of the glass. In addition, the higher the resistance and the larger the thermal expansion coefficient of glass, the larger the resistance change against the external force.

The Basic Reactions, Compositions, and Electrical Properties of Pd-Ag Thick-Film Resistors

The basic reactions, compositions, and electrical properties of glazed Pd-Ag sintered layers through a firing process have been examined by differential thermal analysis, thermograviometric analysis, and X-ray diffraction analysis. The evaporation and combustion of screening vehicle and solvents, the oxidation-reduction behaviors of Pd and Ag the creation of PdAg solid solution, and the electrical properties and stability of these resistors have been studied. From these tests it was found that the degree of process sensitivity for these resistors was high, and electrical properties and stability of these resistors were affected in much the same way by firing temperature and firing period. They were influenced most by temperature rise rate and least by temperature fall rate.

Switching and oscillation phenomena in SnO2‐VOx‐PdO ceramics

Switching and oscillation were found in SnO2‐VOx‐PdO ceramics. This switching does not appear above 60°C. However, under 40°C, it comprises two switching actions and depends upon the ambient temperature. The oscillation is irregular and the amplitude is as great as 30−40 V at room temperature.

New thick‐film strain gauge

Thick‐film strain gauges having strain characteristics with small temperature dependency have been developed. Their gauge factor is more than ten times higher than that of a thin‐film strain gauge and nearly half the value of a semiconductor gauge. This strain gauge is a thick film composed of 15 wt. % WO3⋅15 wt. % RuO2⋅70 wt. % glass (weight percent ratio). Its gauge factor is 40 to 55, its temperature coefficient of resistance is 0 to −200 ppm/°C, and its temperature coefficient of gauge factor is about −400 ppm/°C. The change of gauge factor in a repeat test after a strain had been applied to the gauge was smaller than 1%. The gauge was also very stable.

Mathematical relation between RuO2 volume fraction and resistance of thick-film resistors

The mathematical relation between volume fraction RuO2 and the resistance of RuO2-glazed thick-film resistors has been deduced in terms of the diameters of the RuO2 particles and glass frits and some physical properties of the glass. The equation obtained can qualitatively describe the relation between RuO2 volume fraction and the resistance values. Therefore, valuable information can be obtained for the design of thick-film resistors.