Crystal structure and piezoelectric property of the system Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃ were studied with single crystals and ceramic polycrystals. A PbO-flux method was used for growing the single crystals. Pure Pb(Zn_1/3Nb_2/3)O₃ single crystal has perovskite structure of rhombohedral system. The crystal structure changes to tetragonal when dissolved PbTiO₃ exceeds 10 mol %. Piezoelectric activity increases remarkably in the composition range where the phase change is observed i.e., the electromechanical coupling factor k₃₃ amounts to 75% and the dielectric constant ε₃₃ is 4200. These tendencies are similar to those in the solid solution PbZrO₃-PbTiO₃.
Pb(Zn_1/3Nb_2/3)O₃ ceramic polycrystal has a pyrochlore structure and shows undetectable piezoelectricity. A compound of perovskite structure and that of pyrochlore structure coexist in specimens containing less than 40 mol% PbTiO₃. The coexistence gives rise to extremely low piezoelectric activity.

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The purpose of this investigation is to :elucidate the basic impact properties of sintered iron. Specimens were prepared from electrolytic iron powder (Husqvarna-HVA⋅Star), followed by compacting under 2-9 t/cm², presintering for 30min at 800°C, repressing under 2-9 t/cm² and sintering for lhr at 1200°C in hydrogen. The impact strength was measured on U-notched specimens 8×8×40mm, by a newly designed 7 Kg⋅m-Charpy tester with the distance of 30mm between the specimen supports. Results were summarized as follows.
In sintered iron, as often pointed out, the impact strength increased exponentially as a function of density. And the range of transition temperature was broad. The miciofractographs of sintered irons showed some areas of ductile rupture even in tests at -90°C. These results were considered due to the notch effect of residual pores.
The impact strength of some cast iron was compared with sintered ones. In this respect, it was concluded that the sintered iron with the same density as cast ones was also similar to malleable or nodular cast irons in toughness, and superior to flaky one.
Abnormal brittleness was observed in sintered iron at the density range of 7.0-7.3 g/cc. The details on this brittleness will be described in the next paper.

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As reported in the previous paper, the authors found the abnormal brittleness in high density sintered iron. It appeared at the density range just above 7g/cc, and was different from usual brittleness of low density iron. The present paper is devoted to report the characteristics of this brittleness.
Specimens, 8×8×40mm, were prepared mainly from reduced ore iron powder and partly from others, followed by compacting under 4t/cm², presintering for 30 min at 800°C, repressing under 2-9t/cm² and sintering for 1hr at 1050-1350°C in hydrogen. Impact tests were carried out by the Charpy machine with the supports span of 30mm.
Results were summarized as follows.
Except for carbonyl iron, commercial iron powders showed some abnormal brittleness at the density range of 6.8-7.3g/cc. The brittleness increased accelerated with the rise of sintering temperature.
According to microfractographic observations, this brittleness was presumed mainly as to the grainboundary rupture and partly to the cleavage, while the usual brittleness of lowdensity sintered iron results from transgranular shear rupture through the pores.
It was suggested that the shape of pores and their distribution with respect to grainboundaries are responsible for the mode of rupture.

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For the improvement of mechanical properties of the sintered tungsten compact, the lowtemperature sintering of tungsten powders mixed with a small quantity of Ni-P alloy was investigated.
The results obtained were as follows.
(1) The maximum sintered density and maximum transverse rupture strength were obtained by the addition of Ni-P alloy with, 0.2-0.5% of Ni.
(2) The grain size of the sintered compacts depends upon the quantity of Ni-P alloy and it was maximum at 0.5-1.0% of Ni.
(3) The hardness increased as the quantity of Ni-P alloy increased, and also as the grain size became smaller.
(4) In the case of 0.5μ tungsten powder, the transverse rupture strength had a maximum value at the sintering temperature of 1300-1400°C.
(5) The maximum transverse rupture strength was obtained when 0.5μ tungsten-powder added with Ni-P alloy containing 0.2--1% Ni was sintered at 1300-1400°C.

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Copper powders, lumpish, plate-like, acicular and dendritic were obtained in the reduction of sulphate aqueous solutions with glucose.
Particle shapes are too sensitive to the reducing conditions especially for needles.
Needle-like powders were obtained when a sulfate solution was reduced around 150°C for 30-60 minn and cooled rapidly to room temperature.

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