Hitachi, Ltd.

Mitsuru Ishii

Toshio Kobayashi

Yukio Ito

Kazumasa Takagi

Hiroshi Takeuchi

Tokuumi Fukazawa

Kenzo Susa

Kazuyuki Nagatsuma

Sakichi Ashida

Shigeru Jyomura

Satoshi Taniguchi

Kunio Yamashita

Seigo Kishino

Piezoelectric ceramics containing PbO and TiO.sub.2 as its principal constituents, and further containing 0.5 to 3.7 mol-% of Nd.sub.2 O.sub.3 and 0.2 to 1.5 mol-% of MnO.sub.2. Since the piezoelectric ceramics is low in the dielectric constant and is especially small in the temperature coefficient of the delay of surface acoustic waves, it is suitable for a surface acoustic wave device. Piezoelectric ceramics in which 0.3 to 3.3 mol-% of In.sub.2 O.sub.3 is further added to the above-mentioned composition has a still smaller temperature coefficient of the delay of surface acoustic waves, and it is also possible to make this coefficient zero.

Piezoelectric ceramics

In synthesizing cubic boron nitride from hexagonal boron nitride under high temperature and high pressure conditions, if water is incorporated into the raw material in an amount of at least 3% by weight, cubic boron nitride of a higher purity in the form of smaller crystallites than in conventional products can be obtained under lower temperature and lower pressure conditions than in conventional methods. When graphitic hexagonal boron nitride is used as the raw material, the temperature and pressure necessary for synthesis can be reduced to about 600.degree. C. and 50 Kbar, respectively.

Process for production of cubic boron nitride

In growing single crystals of gadolinium gallium garnet, dysprosium gallium garnet and the like according to the Czochralski method, when the velocity of rotation of the crystal during growth of a slender part is made lower than the velocity of rotation of the crystal during growth of a body portion, single crystals free of defects such as dislocation or facet can be obtained.

Method for producing single crystals

Growing community of inventors

Higashiyamato, Japan

Mitsuru Ishii