Microanalyses on the RuO ₂ Particle–Glass Matrix Interface in Thick‐Film Resistors with Piezoresistive Effects

The piezoresistive mechanisms of composite thick films based on RuO ₂ particles and both calcium‐borosilicate and bismuth‐borosilicate glass matrices were investigated by chemical and electrical microanalyses. The resistor based on bismuth‐borosilicate glass showed higher sensitivity than that based on calcium‐borosilicate glass. It was confirmed that the diffusion of ruthenium into glass affects the binding state of RuO ₂ at the interface of the glass. Furthermore, an intermediate resistive layer is detected around the RuO ₂ particle. These results suggest that the piezoresistive effect is related to a change in the electrical conductivity of the interfacial reaction layer caused by the diffusion of ruthenium into glass.