Regular Article

The temperature dependence of the work function of oxide electrodes in fluorescent lamps

¹ Institut für Physik, Lehrstuhl für Experimentalphysik II, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
² LEDVANCE GmbH (former part of OSRAM AG), Berliner Allee 65, 86136 Augsburg, Germany

^* e-mail: reinhard.langer@physik.uni-augsburg.de
^** Present address: Deutsches Patent- und Markenamt, Zweibrückenstraße 12, D-80331 München, Germany. This article represents the author’s personal opinion and not that of the German Patent and Trademark Office.

Received: 20 December 2019
Received in final form: 30 July 2020
Accepted: 21 August 2020
Published online: 9 October 2020

Abstract

In the present work the temperature dependence of the work function of oxide cathodes in operating fluorescent lamps was investigated experimentally. A detailed review on the theory is presented, including a thermodynamic and a quantum mechanical view on the problem. Aspects such as the role of the electrochemical potential, external and internal potentials, the constituents of the electron affinity, the patch effect and surface states are discussed. For solids in contact the Volta and Galvani potentials are related to their work functions. The importance of colour centres in oxide electrodes on the temperature dependence of the work function and the impact of ultraviolet radiation is emphasized. The measurements have been carried out under zero field emission of electrons from the electrode, using the Waymouth (rf) and Eisenmann (visual) methods as indicators. By inserting an empirical ansatz into the Richardson equation, it was possible to determine the temperature dependence of the work function from the experiments.