Photoacoustic (PA) spectra for Zn1-x Co x O mixed-crystal powders with various Co concentrations and sintering temperatures were measured. The PA spectra showed three peaks of Co2+ absorption between 560 nm and 660 nm. On the other hand, the PA spectra between 800 nm and 1000 nm were almost flat, and these are expected to be dominated by light scattering effects. The PA spectra were normalized by using the Co2+ absorption peaks in order to compare the sample size and the PA signals intensity, and the sintering temperature dependence of the PA spectra is discussed. The PA signal intensity decreased with the increase of the sintering temperature. The decrease of the PA spectra seems to be caused by small light scattering effects for the large clusters under higher temperature sintering, where the grains and clusters size increase. We could evaluate the grain growth in the sintering processes by PA spectroscopy in a noncontact mode.

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Recently, lead free solders have been used in electronic equipments. Sn Ag Cu system is an important alloy for lead free solders. There have been so many reports for mechanical properties of bonding. It is important to understand the evolution of solidified structure of these alloys, though, such reports are few.In order to understand the solidification process of Sn Ag Cu alloys, Sn Ag alloys have been used in this study. Three alloys, hypo eutectic, eutectic, and hyper eutectic alloys have been prepared. The specimen was quenched during solidification and the solidified structure was interrupted and compared with thermal history.In the case of hypo eutectic alloy, the specimen was composed by primary Sn and eutectic. It was found that a small undercooling was necessary for nucleation of eutectic. Such undercooling was not observed in eutectic and hyper eutectic alloys. This may be interpreted by the difference in the liquid composition when the eutectic solidification starts. In the case of eutectic and hyper eutectic alloys, the eutectic as well as b Sn may form at almost the same time of recalescence.In the case of hyper eutectic alloy, it was found that a large undercooling was not necessary for nucleation of Ag 3 Sn, even though it was facetted phase. Since the primary Ag 3 Sn was surrounded by the halo of b Sn and eutectic, the Ag 3 Sn phase may be a site for nucleation of b Sn and eutectic.