【正文】 that the band gap energy for cZrO2 (– eV) is higher pared with mZrO2 (– eV) and tZrO2 (– eV). It is well known that the FTIR spectrums are very use ful techniques for the determination of the crystal phase for ZrO2 (Wang et al., 2022). Moreover, recent reports reveal that ZrO2 matrix is an ideal medium for preparation of highly luminescent materials because it is chemically and photo chemically stable with a high refractive index and low phonon energy (Wang et al., 2022). The FTIR absorption spectrum of recrystallized ZrO2 xH2 O produced after heating at 1000 ? C for 1 h have a group of four bands at 743, 579, 505, 419 cm?1 in ZrO stretching and banding vibrations in ZrO polyhedron, with typical values of = 4 or 6 which is characteristic of the monoclinic phase (Fig. 6a and b). The extended spectrum in the 1000–4000 cm?1 region signi?ed the mesostructure with an amorphous surface of the sample with chemisorbed H2 O molecules. The spectrum in Fig. 6c showed the broad bands at 425, 520 and 750 cm?1 related to cZrO2 phase (Fig. 6c). The trend is consistent with the fact that for cubic ZrO2 only one fundamental mode is active IR and the active modes increase markedly upon lowering the symmetry of the structure by going from cubic to tetragonal and then to monoclinic ZrO2 . Two high broad bands of cZrO2 nanopowders were obtained at 850 and 1500 cm?1 pared with mZrO2 processed by CP and CGC techniques. In general, all ZrO2 polymorphs are very similar in vibrational structure. A minor variation in their band frequencies or intensities infers small differences in the Zr4+ distribution ZrO sites and the oxygen vacancies and other structural defects (Wang et al., 2022。 Hirata et al., 1994。 Feinberg and Perry, 1981). In addition the transmittance spec trum, % was increased in case of cubic ZrO2 nanopowders processed by MRP than the monoclinic ZrO2 nanopowders processed by CP and CGC method. In the present work, the difference of the spectral appearance can be attributed to the transformation of the crystal lattice to a structure with higher symmetry, that is, from tetragonal to monoclinic and then to cubic phase. From the results of UV–visible absorption spec trum and FTIR absorption spectrum, it is clear that cubic ZrO2 phase is favored for technological advanced optical applica tions including on transparent optical devices, optical ?ber connector and photocatalysis pared by mZrO2 . 4. Conclusion ZrO2 nanopowders have been prepared via three process ing routes: precipitation (CP), citrate gel bustion (CGC) and microemulsion re?ned precipitation (MRP). The change in processing routes at different thermally treated tempera tures from 120 to 1200 ? C led to the change of polymorphic phases and properties of the produced ZrO2 nanopowders. Precursors derived from these three processing routes exhib ited very different formation temperature for ZrO2 phases. Directly precipitated precursor and the citrate ZrO2 precursor were given tetragonal ZrO2 phases at 700 ? C which inverted to monoclinic ZrO2 phase at 1000–1200 ? C. On the other hand, MRP technique gave tetragonal ZrO2 phase at 500–700 ? C and cubic ZrO2 phase at 1000–1200 ? C. Amorphous ZrO2 was converted to tetragonal phase at low temperatures for all syn theses techniques and the tetragonal phase is transformed to cubic or monoclinic phase by increasing the temperature, depending on the particular kiic conditions and chemi cal environments. The morphology of zirconia particles was affected by synthesis routes and thermally treated tempera ture. FTIR and UV–visible absorptions of the processed ZrO2 nanopowders formed through three different routes showed that the phase transformation and the synthesis techniques can greatly affect the optical properties of the ZrO2 powders. references Ai, D., Kang, S., 2022. Ceram. Int. 30, 619. Bhattacharjee, S., Syamaprasad, U., Galgali, ., Mohanty, ., 1991. Mater. Lett. 11 (1–2), 59. Botta, ., Navio, ., Hidalgo, ., Restrepo, ., Litter, ., 1999. J. Photochem. Photobiol. A: Chem. 129, 89. Bourell, ., Kaysser, W., 1993. J. Am. Ceram. Soc. 76, 705. Caruso, R., Benavidez, E., de Sanctis, O., Caracoche, ., Rivas, ., Cervera, M., Caneiro, A., Serquis, A., 1997. J. Mater. Res. 12, 2594. Chatterjee, M., Chatterjee, A., Ganguli, D., 1992. Ceram. Int. 18, 43. Djuricic, B., Pickering, S., McGarry, D., Glaude, ., Tambuyser, P., Schuster, K., 1995. Ceram. Int. 21, 1995. Dodd, ., McCormick, ., 2022. J. Eur. Ceram. Soc. 22, 1823. Fang, J., Wang, J., Ng, ., Chew, ., Gan, ., 1997. Nanostruct. Mater. 8 (4), 499. Feinberg, A., Perry, ., 1981. J. Phys. Chem. Solids 42, 513. Galgali, ., Bhattacharjee, S., Syamaprasad, U., 1995. Met. Mater. Processes 7 (2), 121. Hirata, T., Asari, E., Kitajma, M., 1994. J. Solid State Chem. 110, 201. Huang, Y., Guo, C., 1992. Powder Technol. 71, 101. Jiang, Y., Bhide, ., Virkar, ., 2022. J. Solid State Chem. 157, 149. Juarez, ., Lamas, ., Lascalea, ., Walsoe de Reca, ., 2022. J. Eur. Ceram. Soc. 20, 133. Jung, ., Bell, ., 2022. J. Mol. Catal. A: Chem. 163, 27. Kolen’ko, Yu V., Maximov, ., Burukhin, ., Muhanov, ., Churagulov, ., 2022. Mater. Sci. Eng. C 23, 1033. 185 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 5 ( 2 0 0 8 ) 178–185 Kongwudthiti, S., Prasethdam, P., Silveston, P., Inoue, M., 2022. Ceram. Int. 29, 807. Lascalea, ., Lamas, ., Perez, L., Cabanillas, ., Walsoe de Reca, ., 2022. Mater. Lett. 58, 2456. Lee, ., Tai, ., Lu, ., 1999. J. Eur. Ceram. Soc. 19, 2593. Li, C., Yamai, J., Marase, Y., Kato, E., 1989. J. Am. Ceram. Soc. 72, 1479. Liang, J., Jiang, X., Liu, G., Deng, Z., Zhuang, J., Li,