KR100941522B1 - Lead free ceramic composition for ptc thermistor and ptc thermistor thereby - Google Patents

Abstract

Provided is a ceramic composition for a PTC thermistor which does not contain lead (Pb) but can have a low resistivity value at room temperature and a Curie temperature (Tc) of 130 ° C. or higher. The ceramic composition for PTC thermistor according to the present invention is characterized by consisting of any one selected from the following formula (1) and formula (2).

Ba _1-x (Bi _0.5 Na _0.5 ) _x TiO ₃ + y mol% M1 ₂ O _w + z wt% M2O ₂

Ba _1-x (Bi _0.5 K _0.5 ) _x TiO ₃ + y mol% M1O _w + z wt% M2O ₂

(In Formula 1 and Formula 2, 0.01≤x≤0.05, 0.00 <y≤0.40, 0.00 <z≤0.40, M1 is at least one element selected from the group consisting of Nb, Sb, La, Y, M2 is Mn W is 3 if M1 is a trivalent element and 5 if it is a pentavalent element.)

PTC, thermistor, ceramic, BaTiO3, Pb

Description

Ceramic composition for PTC thermistor which does not contain lead component, and PC ceramic thermistor manufactured thereby {lead free CERAMIC COMPOSITION FOR PTC THERMISTOR AND PTC THERMISTOR THEREBY}

The present invention relates to a ceramic composition, and more particularly, to a ceramic composition for PTC thermistor containing no lead component.

The positive temperature coefficient of resistance (PTC) thermistor shows the property that the resistance increases with increasing temperature, and the basic composition is BaTiO ₃ .

BaTiO ₃ (BT) -based semiconducting ceramics are compounds of a typical perovskite-based crystal structure represented by ABO _{3. They} are occupied by divalent Ba ions at A-site and tetravalent Ti ions at B-site. According to the present invention, the crystal structure exhibits a polymorphic property that transitions into a rhomhedral, orthorhombic, tetragonal and cubic system.

The resistance-temperature characteristic is obtained by measuring the electrical resistance of the PTC thermistor at a temperature below 1.5V _DC . In this characteristic, the temperature at which the resistance value increases rapidly is changed to the resistance sudden temperature (switching temperature) or Curie temperature (Curie). Temperature, which is generally defined as the temperature corresponding to twice the minimum resistance value or the reference temperature (25 ° C) resistance value, which is an important parameter of the material properties.

In BaTiO ₃ ceramics, the Curie temperature (Tc) is the temperature of 130 ° C that transitions from the tetragonal phase of the ferroelectric phase to the cubic phase of the phase dielectric. ) Substituted PbTiO ₃ is used.

Lead (Pb) is harmful to the human body and may cause environmental pollution, and lead evaporated in the device may cause deterioration of device uniformity.

The problem to be achieved by the present invention is a PTC thermistor which does not contain lead (Pb) and has a low resistivity value at room temperature, a PTCR effect of 10 ³ or more, a temperature coefficient of 10% or more and a Curie temperature (Tc) of 135 ° C or more. It is to provide a ceramic composition for.

Another object of the present invention is to provide a ceramic PTC thermistor manufactured by using the ceramic composition.

The objects to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The ceramic composition for PTC thermistor according to the present invention for solving the above problems is characterized in that made of any one selected from the following formula (1) and formula (2).

Ba _1-x (Bi _0.5 Na _0.5 ) _x TiO ₃ + y mol% M1 ₂ O _w + z wt% M2O ₂

Ba _1-x (Bi _0.5 K _0.5 ) _x TiO ₃ + y mol% M1O _w + z wt% M2O ₂

(In Formula 1 and Formula 2, 0.01≤x≤0.05, 0.00 <y≤0.40, 0.00 <z≤0.40, M1 is at least one element selected from the group consisting of Nb, Sb, La, Y, M2 is Mn W is 3 if M1 is a trivalent element and 5 if it is a pentavalent element.)

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According to the ceramic composition according to the present invention, a PTC thermistor which may have a low resistivity value, a PTCR effect of 10 ³ or more, a temperature coefficient of 10% or more, and a Curie temperature (Tc) of 130 ° C or higher without containing lead (Pb) at room temperature It will be possible to manufacture.

Specific details of other embodiments will be described in detail.

In the present invention, as a main component of the ceramic composition for PTC thermistor, barium bismuth sodium titanum oxide; Ba _1-x (Bi _0.5 Na _0.5 ) _x TiO ₃ and barium bismuth potassium titanum oxide; Ba _1-x (Bi _0.5 K _0.5 ) _x TiO ₃ -based ceramics were used (0.01 ≦ x ≦ 0.05).

Here the M1O _w, and M2O ₂ was used as a substituent on.

At this time, M1 is a trivalent or pentavalent element, specifically, at least one selected from Nb, Sb, La, Y may be used, and M2 may specifically use Mn as a divalent element.

M1Ow ratio is a ratio which is substituted on the above main component is 0.00 or less than 0.40mol%, M2O ₂ is substituted for the main component is determined in a range of 0.00 or less than 0.40wt%.

In sum, the ceramic composition for PTC thermistor according to the present invention may be represented by any one selected from the following Chemical Formulas 1 and 2.

Ba _1-x (Bi _0.5 Na _0.5 ) _x TiO ₃ + y mol% M1 ₂ O _w + z wt% M2O ₂

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Ba _1-x (Bi _0.5 K _0.5 ) _x TiO ₃ + y mol% M1O _w + z wt% M2O ₂

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(In Formula 1 and Formula 2, 0.01≤x≤0.05, 0.00 <y≤0.40, 0.00 <z≤0.40, M1 is at least one element selected from the group consisting of Nb, Sb, La, Y, M2 is Mn W is 3 if M1 is a trivalent element and 5 if it is a pentavalent element.)

In Formula 1 and Formula 2, 0.01 ≦ x ≦ 0.05, which is because when x is less than 0.01 or exceeds 0.05, a good sintered body cannot be obtained, and thus application to a PTC heater, a PCT current limiter, a PTC resistor, etc. is difficult. Because.

In Formula 1 and Formula 2, it is defined as 0.00 <y≤0.40. The reason is that if y exceeds 0.40, the room temperature resistivity is increased to be difficult to measure, and thus it is difficult to apply to PTC heaters, PCT limiters, PTC resistors, etc. Because.

In Formula 1 and Formula 2, it is defined as 0.00 <z≤0.40. The reason is that if z exceeds 0.40, the room temperature resistivity is increased to such an extent that it is difficult to measure, making it difficult to apply to PTC heaters, PTC current limiters, PTC resistors, and the like. Because.

Hereinafter, in the ceramic composition for PTC thermistors according to the present invention, specific examples and comparative examples will be described with respect to the reason why the x, y, and z values should have the above ranges. Details not described herein are omitted because they can be sufficiently inferred by those skilled in the art.

<Example 1 to Example 33>

TiO ₂ , Bi ₂ O ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , MnO ₂ , BaTiO ₃ were prepared as starting materials, and the raw materials were weighed to form a composition in the range suggested by the present invention.

In each sample, the starting elements were ball milled for 24 hours using a ball mill, and the mixed sample was dried at 100 to 120 ° C., and then the powder was placed in a mortar and pulverized and placed in an alumina crucible at 1000 ° C. 2 hours was calcined.

The calcined powder was put in a mortar again and pulverized, and then wet milled for 24 hours using zirconia balls. Thereafter, the mixed sample was sufficiently dried at 100 to 120 ° C., and then the prepared sample was uniaxially molded into a cylindrical mold (10 mm) at a pressure of 1 [ton / cm ² ] to form a disc-shaped specimen. .

The molded specimens were sintered at 1300 ~ 1350 ° C. for 4 hours, and the temperature increase rate was heated to 1300 ~ 1350 ° C. for 4 hours at 5.4 ~ 5.6 ° C. per minute.

The temperature reduction rate was 100 degreeC / hr, 200 degreeC / hr, and 600 degreeC / hr, and the PTC element was produced.

XRD analysis was performed to analyze the formation of conductive BaTiO ₃ containing TiO ₂ , Bi ₂ O ₃ , and Na ₂ CO ₃ . The PTC device thus produced measured PTC characteristics such as resistance after electrode treatment.

Table 1 below shows the details of chemical quantification of the samples prepared in Examples 1 to 33 and the PTC characteristic measurement results.

1 to 9 are graphs of these measurement results.

< Example  34- Example  53>

A PTC device was manufactured in the same manner as in Example 1, except that TiO ₂ , Bi ₂ O ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , MnO ₂ , and BaTiO ₃ were prepared as starting materials. Details of chemical quantification and PTC characteristic measurement results of the samples prepared in Examples 34 to 53 are shown.

10 to 15 are graphs of these measurement results.

Referring to Table 1 and Table 2 and FIGS. 1 to 15, samples satisfying each condition of 0.01 ≦ x ≦ 0.05, 0 <y ≦ 0.40, and 0.00 <z ≦ 0.40 have a low room temperature specific resistance and a T _c (Curie temperature). It can be seen that exhibits excellent characteristics of 130 ℃ or more.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings and tables, the present invention is not limited to the above embodiments, but may be manufactured in various forms, and common knowledge in the art to which the present invention pertains. Those skilled in the art can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

1 to 9 are graphs of measurement results of measuring PTC characteristics of Examples 1 to 33. FIG.

10 to 15 are graphs of measurement results of measuring PTC characteristics of Examples 34 to 53. FIG.

Claims (3)

Ceramic composition for PTC thermistor consisting of any one selected from formula (1) and formula (2). Ba _1-x (Bi _0.5 Na _0.5 ) _x TiO ₃ + y mol% M1 ₂ O _w + z wt% M2O ₂ Ba _1-x (Bi _0.5 K _0.5 ) _x TiO ₃ + y mol% M1O _w + z wt% M2O ₂ (In Formula 1 and Formula 2, 0.01≤x≤0.05, 0.00 <y≤0.40, 0.00 <z≤0.40, M1 is at least one element selected from the group consisting of Nb, Sb, La, Y, M2 is Mn W is 3 if M1 is a trivalent element and 5 if it is a pentavalent element.) delete PTC ceramic thermistor made from the composition of claim 1.

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