Dielectric material selection
Dielectric resonators. Materials and components

This coefficient τ_f, known as TCF (Temperature Coefficient of Frequency), is essential for devices. Natural materials such as alumina, silicates and titanium oxide have absolute temperature coefficients of several tens of ppm/K, so the user must choose the material whose τ_f enables him to produce a device whose frequency varies as little as possible in its temperature range. The resonator alone does not define this stability, which is modified by the other elements of the circuit (the active element of the oscillator, the cavity, etc.). The resonator's frequency variation in temperature must compensate for that of the environment (see implementation example §