When mechanically excited, initially the ML intensity increases, attains a maximum value and then decreases with time. The total ML intensityIT initially increases with the impact velocityVo of piston and attains a saturation value for higher values ofVo and follows the relationIT=IToexp(−Vc/Vo) whereITo andVc are constants. The ML intensity is maximum for 20% CdS contents in the (Zn, Cd)S phosphors due to increase in hardness which may in turn increase the fracture stress and subsequently the piezoelectric field strength. The wavelength corresponding to the peak of both the ML and PL spectra shift towards longer wavelength with increasing CdS contents. Some models are discussed and it is concluded that the impulsive deformation of these phosphors may be due to piezoelectrification of newly created surfaces. The similarity of ML spectra with EL and PL spectra suggests that although the excitation processes are different, emission process is governed by the states of similar nature.
Volume 42 | Issue 6
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