. The
diffractogram of sample (b) shows two different phases identified
as cubic NiO and hexagonal ZnO which indicate the formation ofthe
composite material. The lattice parameter of NiO is 4.190Å which
is different from the pure NiO (4177Å). This difference again suggests
the partial insertion of Zn into the NiO structure since the
radius of Zn2+ (74 pm) is slightly greater than that of Ni2+ (69 pm)
[48]. This result undoubtedly excludes the formation of a simple
NiO/ZnO composite material, rather favoring the formation of a
Ni1-xZnx/ZnO composite (x ∼0.1) which will be tested for the first
time as gas sensor.