Mg-Zr-O protective films for plasma display panels were deposited on soda-lime glass substrates by magnetron sputtering. The effects of oxygen partial pressure on both the discharge properties (i.e., firing voltage V-f, minimum sustaining voltage V-s, and memory coefficient M-C) and the microstructure of the Mg-Zr-O films were investigated. The results show that the deposited Mg-Zr-O films retain the NaCl-type structure as the pure MgO crystal and the doped Zr exists in the form of Zr4+ substitutional solid solution in MgO crystal lattice. The grain of the films is very fine and the mean grain size is about 7 nm. As the oxygen partial pressure increases from 0.06 to 0.12 Pa, the Zr content increases and surface roughness of the films decreases. However, when oxygen partial pressure further increases, the film shows a decrease in Zr content and an increase in surface roughness. At oxygen partial pressure of 0.12 Pa, the Mg-Zr-O film has the lowest V-f and V-s and the largest M-C, exhibiting the best discharge properties. The improvement of the discharge properties is thought to be related to the energy-band structure and the surface conditions of the Mg-Zr-O films. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3259879]