The kinetics of the triboluminescence of zinc sulphide I

Luminescence induced by elastic deformation of ZnS:Mn nanoparticles

“…These results are in accordance with Eqs. (26), (27), (32) and (35). It is seen that when pressure is released, then the ML emission also takes place.…”

“…The appearance of elastico ML in ZnS:Mn nanocrystals indicates that the local electric field near Mn 2 + ions should be higher because of the local change in the crystals-structure near Mn 2 + sites, where the piezoelectric constant should be higher. The change in the local structure near the impurities has been reported by many workers [17,52] and the possibility of the higher piezoelectric constant near the impurity centres has also been reported [31,32]. If there is nearly 3 to 4 times increase in the piezoelectric constant near the Mn 2 + centres, then the electric field of the order of 10 5 V cm À 1 may be produced, which may cause sufficient decrease in the trap-depth and subsequent electron-hole recombination may release energy non-radiatively for the excitation of Mn 2 + centres.…”

“…The value of (x+ g) determined from the slope of the plot for low value of (t À t m ), using Eq. (32), is found to be 0.61 s À 1 . The value of g determined from the slope of the plot for large value of (t À t m ), using Eq.…”

“…As ZnS crystals are non-centrosymmetric [30], the piezoelectrifiction caused by elastic deformation may give rise to the light emission [22,[31][32][33][34][35][36]. The other possibility for the occurrence of ML in ZnS:Mn nanocrystals may be the electrostatic interaction between charged dislocations and filled electrons traps [1,20,21,[37][38][39][40].…”

“…The crystals of ZnS:Cu and ZnS:Ag do not show elastico ML because the local piezoelectrification near Cu and Ag centres may not be sufficient for causing the detrapping of electrons from the filled electrons traps. Although, in the past many workers [22,[31][32][33][34][35][36] have reported the piezoelectric origin of ML, primarily on the basis of the similarity between the waveforms, spectra, temperature dependence and other characteristics of ML and EL, no attempt has been made regarding the field ionization of traps and impact excitation or ionizations of luminescence centres under internal piezoelectric field. Chudacek [31] has reported that the piezoelectric field produced by the deformations of ZnS crystals is less to cause ML, and he has suggested that the local piezoelectric field near the defect centres may be higher and it may produce ML.…”