Research Development Corporation of Japan

Other

National Institute for Research in Inorganic Materials

Nippon Steel Corporation

Mitsubishi Materials Corporation

Toshiba Ceramics Co., Ltd.

Komatsu Electronic Metals Co., Ltd.

Sumitomo Sitix Corporation

Shigeyuki Kimura

Hitoshi Sasaki

Koji Izunome

Kenji Kitamura

Kazutaka Terashima

Yasunori Furukawa

Atsushi Ikari

Souroku Kawanishi

Shinji Togawa

Shunji Takekawa

Akira Nagashima

Nobuhiro Kodama

Shigeyoshi Kobayashi

Yutaka Shiraishi

Yasuto Miyazawa

Zhang Yi Can

Eiji Tokizaki

Kouji Izunome

Kouichi Koudu

Xingming Huang

Shin-ichi Hanita

Hiroaki Toshima

Nobuo Ii

Xin Ming Huang

A single crystal of lithium niobate or lithium tantalate may be grown from a melt of a composition having a molar excess of Li compared to a melt having the stoichiometric amount of lithium, and having a molar fraction of Li O/(Nb O &plus;Li O) or Li O/(Ta O &plus;Li O) within a range of at least 0.490 and less than 0.500. The single crystal also has at least one element selected from the group consisting of Mg, Zn, Sc and In, in an amount of from 0.1 to 3.0 mol % based on the total amount of the elements, Nb and Li, or the total amount of the elements, Ta and Li.

Single crystal of lithium niobate or tantalate and its optical element, and process and apparatus for producing an oxide single crystal

A stoichiometric single crystal of lithium niobate or lithium tantalate is produced by pulling a single crystal of lithium niobate or lithium tantalate having a molar fraction of Li O/(Nb O &plus;Li O) or Li O/ (Ta O &plus;Li O) of at least 0.490 and less than 0.500, from a melt of a composition having a molar excess of Li over a stoichiometric composition of lithium niobate or lithium tantalate. The single crystal has 0.1 to 3 mol % of at least one element selected from the group consisting of Mg, Zn, Sc and In based on a total amount of elements Nb and Li, or a total amount of elements Ta and Li. The single crystal has substantially no absorption in the visible light region.

In a gas sensor element, an alkali metal ion conductor is provided with a detection electrode comprising an alkali metal carbonate in dissociation equilibrium with CO,gas on one side thereof and a solid standard electrode on the other side thereof. The alkali metal carbonate is bonded to the alkali metal ion conductor via a bonding agent comprising an alkaline earth metal carbonate which is capable of forming an eutectic low-melting composition with the alkali metal carbonate.

Gas sensor element

An iron-doped lithium niobate single crystal having a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of from 0.495 to 0.50 which is closer to the stoichiometrical composition than a usual congruent composition, and a high diffraction efficiency by a two light wave mixture.

Iron-doped lithium niobate single crystal, method for heat treatment

When a Si single crystal 8 is pulled up from a melt 6 received in a crucible 2, the state of eddy flows generated in the melt 6 is judged from the temperature distribution of the melt at the surface. According to the result of judgement, the gas, i.e. N.sub.2, Xe or Kr, which causes extraoridnary deviation in the density of a melt 6 is added to an atmospheric gas, so as to keep the eddy flows under unstabilized condition. The effect of said gas is typical in the case of crystal growth from the melt to which a dopant such as Ca, Sb, Al, As or In having the effect to suppress the extraordinary deviation in the density is added. Since the single crystal is pulled up from the melt held in the temperature-controlled condition at the surface, impurity distribution and oxygen distribution are made uniform along the direction of crystal growth. A single crystal obtained in this way has highly-stabilized quality.

Growth of silicon crystal from melt having extraordinary eddy flows on

When a B or P-doped Si single crystal is pulled up from a B or P-doped melt by the Czochralski method, an element such as Ga, Sb or In having the effect to reduce the heat expansion coefficient of said melt at a temperature near the melting point is added to said melt. The additive element stabilizes the temperature condition of crystal growth so as to control the generation of eddy flows just below the interface of crystal growth. When a Ga or Sb-doped Si single crystal is pulled up from a Ga or Sb-doped melt, an element such as B or P having the effect to increase the heat expansion coefficient of said melt at a temperature near the melting point is added. The agitation of the melt just below the interface of crystal growth is accelerated by the addition of B or P, so as to assure the growth of a Si single crystal from the melt having impurity distribution made uniform along the radial direction. Accordingly, a Si single crystal is formed having a uniform impurity distribution along its lengthwise or radial direction.

Growth of silicon single crystal having uniform impurity distribution

When a single crystal is pulled up from a melt, the difference .DELTA.T between temperatures at the bottom of a crucible and at the interface of crystal growth is controlled so as to hold the Rayleigh constant defined by the formula of:

Growth of silicon single crystal

The amount of Group-V element included in a melt 6 has the close relationship with the oxygen concentration of the melt 6. This relationship is utilized for controlling the oxygen concentration of a single crystal 8 at a high level. The content of Group-V element is calculated from the weight of the melt 6 gauged by a gravimeter 11 and compared with a preset value in a control unit 12. When the calculated content is smaller than the preset value, the control signal to additionally supply Group-V element to the melt 6 is outputted from the control unit 12 to a feeder 14. When the calculated content is larger than the preset value, the control signal to supply a raw material to the melt 6 is outputted to another feeder 13.

Control of oxygen concentration in single crystal pulled up from melt

A Si material mixed with Group-V element is melted in a crucible, and then held in a chamber filled with a rare gas at atmospheric pressure of 100 torr. or higher. A rare gas, e.g. Ar, Kr, Xe or Rn, having a large mass or the mixture of Ar with Kr, Xe or Rn may be used as atmospheric gas. The high-pressure atmosphere suppress the evaporation of oxides of Group-V elements from the Si melt, so that the Si melt can be maintained at a high oxygen concentration under a stable condition until the start of pulling operation.

Preparation of silicon melt for use in pull method of manufacturing

The density of a melt precisely represents the stability of the melt, so that the initiation of pulling-up operation can be determined on the basis of the changing rate of the density. The pulling-up operation may be started when the density becomes constant, or when the changing rate of the density with respect to the temperature becomes smaller. Since the melt or clusters do not include different minute structures, an obtained single crystal is of high quality free from minute faults or dislocations.

Pull method for growth of single crystal using density detector and

A gadolinium-lutetium-gallium garnet crystal having the formula:

Growing community of inventors

Tsukuba, Japan

Shigeyuki Kimura