Pressing conditions for briquetted bodies based on materials in the system ZnO-TiO₂

Conclusions

In the manufacture of ceramic semiconductors based on zinc oxide and titanium dioxide it is desirable to add prebriquetted material to the bodies. This markedly reduces the shrinkage and somewhat increases the stability of the properties of the materials obtained.

The optimum conditions of semidry pressing briquetted bodies are as follows:

briquette content 70%; a lower content does not greatly affect the reduction in shrinkage nor improve the other factors; and a bigger content seriously impairs the ceramic properties; the specific resistance depends very little on the briquette content; the optimum firing temperature is about 1200°;

3% aqueous solution of polyvinyl alcohol can be sucessfully used as a bond for semidry pressing; the optimum amount is 8–9%;

the optimum pressure is 500–600 kg/cm²; a change in pressure in the limits of 300–800 kg/cm² has little effect on the properties of the fired material; the compaction of the material with a change in pressure from 300 to 1200 kg/cm obeys the rule formulated by Berezhnoi (ɛ = a − b log P); with higher pressures the true porosity of the green specimens does not approximate to this equation;

observation of these conditions for making semiconductors permits a marked reduction in the variations of their ceramic properties and to a certain degree in the specific resistance.