Study of the electrical properties of zirconia heaters at temperatures up to 2100°C

Conclusions

Studies were made of the electrical characteristics of zirconium dioxide heating elements. With a change in the electrical load on the element, causing a change in the temperature by 150–300°C, the thermal equilibrium of the system is in practice stabilized for the specified furnace design in a period of 1 h. The electrical resistance in this case drops smoothly, asymptotically approximating to the values typical for equilibrium conditions. The rating on the heating element at the moment of raising the current strength increases, and then drops smoothly as a function of the change in the resistance of the heater.

The temperature at the surface of the element changes as a function of the current density according to a law close to linear, independently of the nature of the stabilizing additive.

The heating element containing cerium oxide is distinguished by a relatively low rating compared with the elements containing CaO and Y₂O₃, but the nonlinearity of the relationship with temperature and the rating makes its use less desirable as a result of the great complexity of control.

The volt-ampere characteristics suggest that the control of the working cycle of the heating element should be made with respect to the current strength, which will ensure the possibility of controlling the heating elements based on zirconium dioxide which are characterized by a negative temperature coefficient of resistance.