Hydrogen-induced degradation in NiCuZn ferrite-based multilayer chip inductors

Hydrogen-induced degradation in Ni0.38Cu0.12Zn0.50Fe2O4-based multilayer ceramic chip inductors was studied through an electrochemical hydrogen charging method, in which the silver electrodes of the inductors were made a cathode in 0.01 M NaOH solution to evolve hydrogen by the electrolysis of water. After the treatment, the inductance and the quality factor of the inductors at high frequencies were dramatically decreased. The degradation showed a little spontaneous recovery at room temperature and could be mostly recovered through a heat-treatment of 4 h at 250 °C in N2. It is proposed that hydrogen generated by the electrolysis of water is incorporated into the ferrite lattice and exists as an interstitial proton after reducing Fe3+ to Fe2+. The stability of hydrogen in ferrites decreased with increasing temperature and its outdiffusion resulted in the recovery. Hydrogen-induced degradation is important to ferrite-based chip inductors in fabrication and in operation.