Noritake Co., Ltd.

Mitsubishi Rayon Engineering Co., Ltd.

Hiroshi Inada

Yoshihisa Ito

Yoshihisa Yamada

Takao Yamada

Kiyoko Ban

Masanori Hirano

Motoyuki Inoue

Tadao Kamiya

Takayuki Yoshikawa

Shigeru Takane

Keizo Ichii

Kiyoshi Sukai

Provided is a high-strength zirconia sintered body in which the progression of low-temperature degradation is inhibited. The zirconia sintered body contains partially-stabilized zirconia as a matrix phase and contains at least one element from among phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The content of the abovementioned element(s) in the zirconia sintered body ranges from 4&#xd7;10mol to 4&#xd7;10mol with respect to 1 mol of zirconium(IV) oxide. Preferably, the zirconia sintered body further contains 0.03% to 3% by mass of silicon dioxide.

Zirconia sintered body, and mixture, pre-sintered compact and pre-sintered calcined body for sintering zirconia sintered body

A dental porcelain material free of yellow coloring or opacification upon firing is produced. A powder mixture is prepared by adding 0.1 to 2.0 wt % of antimony trioxide and 0.01 to 5 wt % of nitric acid or its salt or salt, to a porcelain starting material. The powder mixture is heat-treated at a temperature not lower than the softening temperature of the powder mixture to produce a fused mass which is pulverized and water-washed. 0.01 to 5 wt % of nitric acid or its salt or salts may be added again during the pulverizing step.

Dental porcelain material preventing yellow coloration and method for

The invention consists of zirconia base with high hydrothermal stability which: (a) consists essentially of at least 40 weight % of partially stabilized zirconia of the ZrO.sub.2 -Y.sub.2 O.sub.3 -CeO.sub.2 system wherein the proportion of ZrO.sub.2, Y.sub.2 O.sub.3, and CeO.sub.2 is within the range defined by the line connecting points F, G, L, M, N and K in a ternary diagram (ZrO.sub.2, YO.sub.1.5, CeO.sub.2), the vertices of said points being given by the following molar % of ZrO.sub.2, YO.sub.1.5, and CeO.sub.2, respectively:

Zirconia base ceramics

The outer periphery of a screw and the inside of a barrel of a screw type extruding or kneading machine are made of ceramics, to improve the abrasion and heat resistances thereof, so that the screw and the barrel will operate for a longer life time even if a hard material or a material containing a hard material is worked.

Screw type extruding or kneading machine and screw used therein

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Nagoya, Japan

Hiroshi Inada