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The cathodoluminescent characteristics of phosphor screens excited by cold electrons from field emitter arrays can be influenced by the resistivity of the phosphor screen. The resistivity of ZnGa 2 O 4 :Mn phosphor screens was determined experimentally and the correlation between the screen resistivity and the luminance was obtained. Addition of WO 3 to ZnGa 2 O 4 :Mn phosphor was one way of controlling the resistivity, and subsequently the luminance. In field emission displays ͑FEDs͒, the resistivity of the phosphor screen gives rise to a voltage drop on the anode side and modifies the emission characteristics of emitters, which leads to a negative effect on the luminance. The luminance has been generally expressed as LϭI anode V anode . But with the resistivity of the phosphor screen taken into consideration, it should be expressed as LϭI anode V phosphor . For either reason, the resistivity of the phosphor needs to be held as low as possible to get the maximum luminance out of FED. Experiments show that the resistivity of ZnGa 2 O 4 :Mn phosphor is typically 10 10 ⍀ cm.

There is a requirement for a simple and accurate extension sensing method for multilayer piezoelectric actuators for precision micro-positioning applications. This paper explains three different techniques of extension sensing for multilayer piezoelectric actuators, to provide a suitable method which involves primarily overcoming the inherent hysteretic behaviour of piezoelectric materials. The methods were; time domain ultrasonic pulse echo response for time travel of acoustic pulses, frequency shift response spectrum of an ultrasonic transducer and frequency shift in the impedance spectrum of the actuator alone. From the results, method of the frequency shift in the impedance spectrum of the actuator alone proved to be the most effective of the three. It was found that due to acoustic velocity changes under DC bias during the ultrasonic measurements, the inherent hysteretic behaviour was amplified in the other two methods when extension was plotted against time-shift and frequency shift. The results are presented and are discussed in terms of their suitability for precise positioning.