MgO powders for protective layer of alternating current plasma display panel

The MgO powder used for a screen-printed protective layer on plasma display panels was evaluated. The MgO powder was formed by either vapor-phase oxidation or decomposition of Mg(OH)₂. For the same BET value, the diameter of MgO particles formed by the latter method was larger than that by the former method. It was found that the particle diameter calculated by Scherrer's equation using the half-value width of an X-ray diffraction pattern was less than one-fifth of that calculated using the BET value. When the distribution of the particle size was evaluated by the centrifuge precipitation method, it was found that both the median and modal diameters of die MgO powders formed by the latter method were larger than that by the former method. The powder formed by the latter method also contained powder with diameters of less than 20 nm; the weight ratio of the fine powder to the entire MgO powder was 5.5 ∼ 15.9 wt%. The transmission electron microscopy (TEM) observation revealed that the powder formed by the former method had a higher crystallinity and that the powder formed by the latter method tended to aggregate. When protective MgO layers were fabricated by sintering MgO powder formed by the above two methods, the powders oriented in the (111) orientation and the MgO formed by the former method had a higher crystallinity. It was concluded that, since the MgO powder formed by the former method (vapor phase method) had a finer particle diameter, higher crystallinity, and higher uniformity than the powder formed by the latter method (decomposition of Mg(OH)₂), the MgO powder formed by the former method is more suitable for the alternating current plasma display panel (AC-PDP) printed protective layer.