Abstract
Pyroelectric crystal is spontaneously polarized material. The polarization varies by varying temperature and the compensating charges appear on the surface. The high-energetic electron can be obtained by using this crystal. Thus radiation source which is very compact can be made without high-voltage generating device. Several studies of the radiation source using pyroelectric crystal have been performed, but basic data to control the radiation source had not been examined. In this study, we measured the charges emitted from pyroelectric crystal with the parameters of the temperature ramp rate and the pressure to obtain basic data to control the electron emission. Here, temperature ramp rate means temperature variation with respect to time. We used LiTaO3 crystal as pyroelectric crystal. LiTaO3 crystal was in size of 10×10×0.5 mm. We used the heater of 78 Ω. Temperature was varied from room temperature to about 70 °C by varying heater current (0.2, 0.3, and 0.4 A). Thus, the temperature ramp rate was the range of 0.4-1.5 K/s. The pressures were 15, 20, and 25 Pa by using rotary pump. While varying the temperature ramp rate, we measured the charges emitted from pyroelectric crystal for 30 sec for three times. When the averages of the temperature ramp rate were 0.4, 0.9, and 1.5 K/s at 20 Pa, the averages of the emitted charge were 73, 259, and 494 nC, respectively. This shows that the emitted charge increases as the temperature ramp rate increases. When the pressures were 15, 20, and 25 Pa at 1.5 K/s, the averages of the emitted charge were 157, 494, and 492 nC, respectively. The emitted charge at 20 Pa was almost same as that at 25 Pa. Compared with the pressures of 20 Pa and 25 Pa, the emitted charge was considerably low at 15 Pa. This result shows that when pressure is too low, it is hard for the electron to emit.
