  Different samples of Zn1-xMnxO series have been prepared by conventional
solid state sintering method. It has been identified, up to what extent of
doping enable us to synthesize single-phase polycrystalline Mn doped ZnO
samples which is one of the prerequisite for dilute magnetic semiconductor and
we have analyzed its certain other physical aspects. In synthesizing the
samples proportion of Mn varies from 1 at% to 5 at%. However the milling times
have been varied (6, 12, 24, 48 & 96 hours) for only 2 at% Mn doped samples
while for other samples (1, 3, 4 & 5 at% Mn doped) the milling time has been
kept fixed at 96 hours. Room temperature X-Ray diffraction (XRD) data reveal
that all of the prepared samples up to 3 at% of Mn doping exhibit wurtzite-type
structure, no segregation of Mn and/or its oxides has been found. The 4 at% Mn
doped samples show a weak peak of ZnMn2O4 apart from usual other peaks of ZnO
and the intensity of this impurity peak has been further increased for 5 at% of
Mn doping. So beyond 3 at% doping single-phase behavior is destroyed. Band gap
for all the 2 at% Mn doped samples have been estimated as between 3.21 to 3.19
eV and reason for this low band gap values has been explained through the grain
boundary trapping model. The room temperature resistivity measurement shows
increase of resistivity up to 48 hours of milling and with further milling it
saturates. The defect state of these samples has been investigated by using
positron annihilation lifetime (PAL) spectroscopy technique. Here all the
relevant lifetime parameters of positron i.e. free annihilation (tau 1), at
defect site (tau 2) and average (tau av) increases with milling time.
