Hitachi Metals, Ltd.

Sumitomo Special Metals Co., Ltd.

Hitatchi Metals, Ltd.

Kazuya Toji

Takeshi Shimada

Kazuhiro Nishikawa

Koichi Terao

Kazuhiro Kura

Kei Matsumoto

Tomoyuki Tada

Shugo Ohtsuki

A semiconductor porcelain composition is prepared by separately preparing a composition of (BaR)TiO(R is La, Dy, Eu, Gd or Y) and a composition of (BiNa)TiO, and calcining the composition of (BaR)TiOat a temperature of 900&#xb0; C. through 1300&#xb0; C. and calcining the composition of (BiNa)TiOat a temperature of 700&#xb0; C. through 950&#xb0; C., and then mixing, forming and sintering the calcined powders. Similarly, a semiconductor porcelain composition is prepared by separately preparing a composition of (BaM)TiO(M is Nb, Ta or Sb) and a composition of (BiNa)TiO, and calcining the composition of (BaM)TiOat a temperature of 900&#xb0; C. through 1300&#xb0; C. and calcining the composition of (BiNa)TiOat a temperature of 700&#xb0; C. through 950&#xb0; C., and then mixing, forming and sintering the calcined powders.

Semiconductor porcelain composition and method of producing the same

It is intended to provide a Pb-free semiconductor ceramic composition capable of shifting its Curie temperature toward a positive direction and capable of enhancing its jump characteristic while minimizing the increase in the resistivity at room temperature. There is provided a semiconductor ceramic composition in which a part of Ba of BaTiOis substituted with Bi&#x2014;Na, the semiconductor ceramic composition being obtained by sintering a mixed calcined powder containing a calcined BT powder containing a calcined powder of (BaR)TiOor a calcined powder of Ba(TiM)O(in which R and M each are a semiconductor dopant), and a calcined BNT powder containing a calcined powder of (BiNa)TiO; in which BaCOand/or TiOis/are added to the calcined BT powder or the calcined BNT powder or to the mixed calcined powder.

Semiconductor ceramic composition and method for producing the same

It is intended to provide a semiconductor ceramic composition containing no Pb, which is capable of shifting the Curie temperate to a positive direction as well as of controlling room temperature resistivity and having an excellent jump characteristic. Since the semiconductor ceramic composition in which a portion of Ba of BaTiOis substituted by Bi&#x2014;Na has a crystal in which a central part and an outer shell part of a crystal grain are different from each other in composition, the composition is capable of improving control of room temperature resistivity and a jump characteristic, and therefore it is optimum as a material for a PTC thermistor, a PTC heater, a PTC switch, a temperature detector, and the like.

Semiconductor ceramic composition

It is intended to provide a semiconductor ceramic composition in which a part of Ba in BaTiOis substituted with Bi&#x2014;Na, which is capable of restraining the evaporation of Bi in the calcination step, is capable of restraining the compositional deviation of Bi&#x2014;Na thereby suppressing the formation of different phases, is capable of further reducing the resistivity at room temperature, and is capable of restraining the fluctuation of the Curie temperature; and to provide a production process of the same. When a calcined Ba(TiM)Opowder (M is a semiconductor dopant) and a calcined (BiNa)TiOpowder are separately prepared and the Ba(TiM)Opowder is calcined at a relatively high temperature while the (BiNa)TiOpowder is at a relatively low temperature, both at the most suitable temperatures for them, then the evaporation of Bi may be retarded and the compositional deviation of Bi&#x2014;Na may be thereby suppressed to inhibit the formation of different phases; and when these calcined powders are mixed, formed and sintered, then a semiconductor ceramic composition which has a low resistivity at room temperature and is capable of restraining the fluctuation of the Curie temperature can be obtained.

Semiconductor ceramic composition and process for producing the same

The invention intends to provide a dielectric porcelain composition for use in electronic devices, in which the relative dielectric constant &#x2208;r is high, the Qf value is high and, the temperature coefficient &#x3c4;f can be controlled while maintaining the temperature coefficient &#x3c4;f at the resonant frequency small and the Qf value high. According to the invention, when, in an LnAlO&#x2014;CaTiO-based dielectric porcelain composition, a molar ratio of LnAlOand CaTiOis optimized and Al is substituted by a slight amount of Ga, a structure that has an LnAlO&#x2014;CaTiOsolid solution as a main phase and a solid solution of Al&#x2014;Ga-based oxide as a secondary phase and does not substantially contain &#x3b1;-AlOin the structure can be obtained, and the temperature coefficient &#x3c4;f can be controlled while maintaining the temperature coefficient &#x3c4;f at the resonant frequency small and the Qf value high.

Dielectric porcelain composition for use in electronic devices

It is intended to provide a semiconductor ceramic composition capable of shifting the Curie temperature to a positive direction as well as of obtaining an excellent jump characteristic while suppressing an increase in room temperature resistivity to a minimum value. There is provided a semiconductor ceramic composition in which a portion of Ba of BaTiOis substituted by Bi&#x2014;Na, the semiconductor ceramic composition being obtained by sintering a mixed calcined powder of a BT calcined powder containing (BaR)TiOor Ba(TiM)O(wherein each of R and M is a semiconductive dopant), wherein a part of BaCOand TiOare remained therein; and a BNT calcined powder containing a (BiNa)TiOpowder.

The invention intends to provide, in BaTiOsemiconductor porcelain composition, a semiconductor porcelain composition that, without using Pb, can shift the Curie temperature to a positive direction and can significantly reduce the resistivity at room temperature. According to the invention, when Ba is partially substituted by an A1 element (at least one kind of Na, K and Li) and an A2 element (Bi) and Ba is further substituted by a specific amount of a Q element, or when Ba is partially substituted by an A1 element (at least one kind of Na, K and Li) and an A2 element (Bi) and Ti is partially substituted by a specific amount of an M element, the optimal valence control can be applied and whereby the resistivity at room temperature can be significantly reduced. Accordingly, it is optimal for applications in a PTC thermistor, a PTC heater, a PTC switch, a temperature detector and the like, and particularly preferably in an automobile heater.

Semiconductor porcelain composition

A semiconductor porcelain composition [(BiNa)(BaR)]TiOwith 0&#x3c;x&#x2266;0.2, 0&#x3c;y&#x2266;0.02 and R being selected from the group consisting of La, Dy, Eu, Gd or Y is prepared by separately calcining a composition of (BaR)TiOat a temperature of 900&#xb0; C. through 1300&#xb0; C. and calcining a composition of (BiNa)TiOat a temperature of 700&#xb0; C. through 950&#xb0; C., and then mixing the two calcined powders and forming and sintering the mixed calcined powder. Similarly, a semiconductor porcelain composition [(BiNa)(Ba][TiM]Owith 0&#x3c;x&#x2266;0.2, 0&#x3c;z&#x2266;0.005 and M being selected from the group consisting of Nb, Ta and Sb is prepared by separately calcining a composition of (BaM)TiOat a temperature of 900&#xb0; C. through 1300&#xb0; C. and calcining a composition of (BiNa)TiOat a temperature of 700&#xb0; C. through 950&#xb0; C., and then mixing the two calcined powders, and forming and sintering the mixed calcined powders.

A method of producing a semiconductor disk represented by a composition formula [(BiNa)(BaR)]TiO, in which R is at least one element of La, Dy, Eu, Gd and Y and x and y each satisfy 0&#x2266;x&#x2266;0.14, and 0.002&#x2266;y&#x2266;0.02 includes carrying out a sintering in an inert gas atmosphere with an oxygen concentration of 9 ppm to 1% and wherein a treatment at an elevated temperature in an oxidizing atmosphere after the sintering is not carried out.

Method of producing semiconductor porcelain composition

A dielectric ceramic composition for microwave use having a relative permittivity &egr;r of 35 to 45, Qf value of more than 50,000 GHz (at 7 GHz), and dielectric characteristic of &tgr;f&equals;0&plusmn;10 ppm/&deg; C includes an La O .Al O .SrO.TiO based ceramic composition and a specific quantity of Ga O to increase the Qf value and a specific amount of Pr O to control the &tgr;f value.

Dielectric ceramic composition for microwave use

A method for producing X(Ba .Sr )(Zn .(Ta .Nb ) )O &mdash;Y(Ba .Sr )(Ga .Ta )O solid solution system, characterized in that sintering is carried out at a temperature of 1400&deg; C. to 1550&deg; C. in an atmosphere of N containing oxygen in a concentration of 6% to 40% or sintering is carried out at a temperature of 1400&deg; C. to 1550&deg; C. after presintering at a temperature of 900&deg; C. to 1300&deg; C. This method is suitably used in order to constantly produce a dielectric porcelain composition for an electronic device which has a reduced temperature coefficient of resonance frequency and an excellent specific dielectric constant, and is uniform with respect to the quality distribution in one composition, by suppressing the evaporation of the Zn contained in a conventional porcelain composition of a perovskite type compound and adjusting the oxygen concentration in an atmosphere for sintering to a specific value without controlling a composition.

Method for producing dielectric porcelain composition for electronic device

A dielectric ceramic composition for electronic devices, which exhibits &tgr;f and &isin;r characteristics equivalent or superior to those of the dielectric ceramic composition of the prior art, can inhibit the evaporation of Zn from the composition to thereby facilitate the control of makeup of the composition, can give homogeneous ceramics through short-time sintering more stably, is improved particularly in permittivity (Qf) and controllability of temperature characteristics, and permits downsizing of the dielectric elements. This composition is a solid solution of XBa(Zn,.Ta,)O,&mdash;Y(Ba,.Sr,)(Ga,.Ta,)O,which contains a specific trivalent metal ion and has a Zn content adjusted to a predetermined level, wherein part of Ta contained in the XBa(Zn,.Ta,)O,moiety has been replaced by Nb. The composition is improved not only in permittivity by virtue of the above replacement but also in the degree of sintering by virtue of the above trivalent metal, i.e., Ga contained in the Y(Ba,.Sr,)(Ga,.Ta,)O,moiety, thus attaining the effects of improvement in permittivity and control of temperature characteristics simultaneously.

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Osaka, Japan

Kazuya Toji