It can be observed from figure that upon increasing the sintering temperature from 1000 °𝐶 to 1400 °𝐶 apparent density increased. Conventionally sintered pellets at 1500 °𝐶 and 1600 °𝐶 showed the highest densification followed by a plateau . However, some ceramics oxides showed a reverse densification behavior which after a point density decreases due to partial formation of liquid phase . However, sintering at 𝑇 ≥ 1500 °𝐶 resulted in excessive grain The obtained powder X-ray diffraction (XRD) patterns of the as-sintered pellets at 1000 °𝐶 to 1650 °𝐶 for 6 hours were collected at room temperature and presented in a comparative stack plot in figure . The crystal structure and lattice constant were determined from the XRD pattern using the Rietveld method implemented with GSAS-𝛪𝛪 software . The average crystallite size was determined from the (111) reflection of the fluorite structure using the Scherrer equation 𝜏 = 𝜅𝜆 𝛽. 𝑐𝑜𝑠𝜃 where 𝜏 is the mean size of the crystalline domains, 𝜅 is shape factor and dimensionless (typically 0.94 ), 𝜆 is the wavelength of radiation, 𝛽 is the full width (line broadening) at half maximum intensity (FWHM) in radians, and 𝜃 is the Bragg angle in radians. It is noteworthy that the shape factor of the XRD peak profiles could be fit by either Gaussian (for rounded tops typically due to strain broadening) or Lorentzian (for sharper tops due to size distribution and dislocations) distributions. The peak shapes of the experimental data Typically follow Voigt distribution which is a convolution of Gaussian and Lorentzian peak shapes where both contributions are equally weighted which resulted to shape factor 0.94 instead of Scherrer's original shape factor value of 0.88 or 0.9. The calculated crystalline size and the lattice parameters can be found in table I. The calculated crystallite size is observed to improve with sintering temperature for all samples from 28 nm to 89 for sintering at 1000 and 1650 respectively for 2 hours. ) which 𝑡΄ and 𝑡΄΄ can be formed due to the presence of distorted oxygen sublattice in the cubic (fluorite) environment . The XRD data suggested that depending on sintering temperature and time, three phases of cubic, tetragonal and monoclinic were detected. The XRD pattern suggested formation and coexistence of the cubic and tetragonal structure for samples sintered at 𝑇 > 1200 °𝐶. However, evidence of formation monoclinic phase next to cubic and tetragonal structures were observed in the sample sintered at 𝑇 < 1200 °𝐶. The samples sintered at 1000 °𝐶 and 1100 °𝐶 contained a distinguished (11 © 1) peak of monoclinic at ~28° as given in figure . The volume fraction of the monoclinic phase was calculated to be in the range of 𝑋 G < 7%. Generally the monoclinic phase formation in zirconia systems depends on the primary sample preparation methods, the sintering conditions, and even following mechanical treatments such as surface polishing/grinding . Therefore, to minimize the effect of the powder XRD samples' preparations, the XRD was carried out on the as-sintered pellets placed on a p-type B-doped silicon zero diffraction plate, and no grinding process had been done.