Role of Ni²⁺ in transparent glass-ceramics with semiconductor nanocrystals for optoelectronic applications

Phosphate glass doped with 5 wt% Ni²⁺ ions and glass-ceramics containing ZnTe nanocrystals with x wt% of Ni²⁺ ions (x = 0.5, 1.0, 5.0 and 10.0) were prepared by fusion method. The structural analyses were performed through XRD, FTIR-ATR and Raman techniques. The XRD revealed amorphous and ZnTe crystalline phases. Several phosphate groups were observed from FTIR-ATR and Raman spectra showing that Ni²⁺ ions possess octahedral symmetry. The intensity of the1352 nm band increased with the increase of Ni²⁺ ions in GC which is an indicative of the ⁶Ni²⁺ coordination. The emission cross-sections (s_emi), full width at half maxima for the ¹T_2g(D)→³T_2g(F) and ³T₂(F)→³A₂(F) emissions were reported. The product of s_emi and t_m (figure of merit) and s_emi (³T₂(F)→³A₂(F) ) was higher to GC sample with 10.0 wt% of Ni²⁺. Thermal diffusivity (D) and thermal conductivity (K) were obtained through thermal lens and thermal relaxation methods. D and K did not change significantly with the increase of Ni²⁺ ions (0.5 – 5 %) in GCs. The 10.0 wt% Ni²⁺ sample presented the lower variation of the optical path with temperature with good lasing properties suggesting it as good candidate for optoelectronic applications.