Dielectric and spectroscopic features of ZnO-ZnF2-B2O3:MoO3 glass ceramic-a possible material for plasma display panels

ZnO-ZnF2-B2O3 borate glass mixed with different concentrations of MoO3 were synthesized and subsequently crystallized. The X-ray diffraction studies revealed that the samples were embedded with crystalline phases in which molybdenum ions exist in Mo6+ and Mo5+ states. The results of spectroscopic studies (viz., optical absorption and electron spin resonance) have revealed that the there is an increasing proportion of Mo5+ ions with increase in the concentration of MoO3 in the glass ceramic. The results of photoluminescence spectra have indicated that if the care is taken to minimize Mo5+ ion concentration, these glass ceramics are suitable for light emission in the blue, green and red regions. The analysis of the results of IR spectra have indicated that with increase in the content of MoO3 there is an increasing degree of disorder in the glass network. The room temperature dielectric constant of these glass ceramics containing even the highest concentration of MoO3 is always found to be in between 11.5 and 12.4 suggesting that these glass ceramics would be suitable for dielectric layer in plasma display panels (PDP). The dielectric parameters have exhibited relaxation character; the relaxation effects have been attributed to molybdenyl complexes. The observed increase in the electrical conductivity with MoO3 content is attributed to the contribution of polaronic transfer between Mo5+ <-> Mo6+ ions. Additionally, the substantial decrement in jump distance for zinc ions between the two sites in the ceramic network (because of increase in the concentration of dangling bonds) is also found to contribute to the conductivity. The value of dielectric breakdown strength for the studied materials is measured to be in the range of 10.54-12.9 kV/cm which is far greater than the required value for a material to be used as dielectric layer in PDP.