Ispitivanje sinterovane cink-kalaj-oksidne keramike fotoakustičnom spektroskopijom

Abstract

Prahovi ZnO i SnO2 pomešani u molamom odnosu 2:1 mehanički su aktivi- rani u planetamim mlinu sa kuglama u intervalu od 10 do 160 minuta. Do- bijene smeše presovane su i izotermski sinterovane na 1300 °C, dva sata. Uzorci su analizirani primenom rendgenostruktume analize, mikrostmktume analize i fotoakustične spektroskopije. Fotoakustični (FA) fazni i amplitudski spektri sinterovanih uzoraka snimljeni su u funkciji čopovane frekvencije upotrebljenog laserskog zračenja (crveni laser snage 25 mW, λ = 632 nm) u toplotno-transmisionoj konfiguraciji. Teorijska analiza eksperimentalnih rezultata FA merenja na osnovu Rosencvvaig-Gersho termalno-klipnog mode- la omogućila je izračunavanje toplotne dijuzivnosti, D (m2s-1), difuzionog koeficijenta manjinskih slobodnih nosilaca, D (m2s-1) i optičkog apsorpci- onog koeficijenta (m-1)

In this paper the changes that occured in differently activated ZnO-SnO(2) and sintered samples were investigated using photoacoustic spectroscopy. ZnO and SnO(2) powders, mixed in the molar ratio 2:1, were mechanically activated in a planetary ball mill for 10-160 min. The mixtures were pressed and isothermally sintered at 1300 degrees C for two hours. X-ray diffraction analysis of the obtained sintered samples was performed in order to investigate changes of the phase composition and confirmed only the presence of a pure zinc stannate (Zn(2)SnO(4)) phase in all the sintered samples as a result of the solid state reaction and reaction sintering between the starting ZnO and SnO(2) powders. The microstructure of the sintered samples was examined by scanning electron microscopy and showed that mechanical activation leads to the formation of a structure with reduced particle size which accelerates spinel formation. Grain growth of the spinel phase slows down the densification process and together with the agglomerates formed during mechanical activation causes the appearance of a porous microstructure. The photoacoustic (PA) phase and amplitude spectra of the sintered samples were recorded as a function of the chopped frequency of the laser beam used (red laser with a power of 25 mW, lambda = 632 nm) in a thermal-transmission detection configuration. PA experimental data were analyzed using the Rosenzweig-Gersho thermal-piston model, which enabled determination of the thermal diffusivity, D(T) (m(2) s(-1)), diffusion coefficient of the minority free carriers D (m(2)s(-1)) and the optical absorption coefficient (m(-1)). The detected differences of the measured thermal-electrical properties of the obtained Zn(2)SnO(4) ceramics indicate changes in the material induced by the different preparation procedure of the starting powders before the sintering process.