JPS6224381B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porcelain composition, particularly a porcelain composition that can be sintered at a low temperature of 1050° C. or lower, has a high dielectric constant, has a high insulation resistance at room temperature and high temperature, and has high mechanical strength. It is well known that ceramics containing barium titanate (BaTiO ₃ ) as a main component have been widely put into practical use as dielectric ceramic compositions. However, those whose main component is barium titanate (BaTiO ₃ ) have a sintering temperature of usually 1300 to 1400°C. Therefore, when using this material in a multilayer capacitor, a material that can withstand this sintering temperature must be used for the internal electrodes, such as an expensive noble metal such as platinum or palladium, which has the disadvantage of high manufacturing costs. be. In order to make multilayer capacitors cheaply, it is necessary to use porcelain that can be sintered at as low a temperature as possible, especially below 1050°C, so that inexpensive metals such as silver and nickel can be used for the internal electrodes. Furthermore, the electrical properties of the ceramic composition are basically required to have a high dielectric constant, low dielectric loss, and high insulation resistance. Furthermore, regarding the value of insulation resistance, MIL-C-55618B of the Military Specification, a US Department of Defense standard that requires highly reliable components, specifies not only the value at room temperature but also the value at 125°C. As stated above, in order to obtain a highly reliable ceramic capacitor, it is necessary to have a high insulation resistance value not only at room temperature but also at the maximum operating temperature. In addition, in the case of multilayer chip capacitors, when the chip capacitor is mounted on a board, mechanical strain is applied to the chip capacitor due to the difference in thermal expansion coefficient between the board and the porcelain that makes up the chip capacitor. This may cause cracks or damage. Furthermore, even in the case of dip capacitors coated with epoxy resin or the like, cracks may occur in the dip capacitor due to the stress of the coating resin. In either case,
The lower the mechanical strength of the porcelain forming the capacitor, the easier it is to crack and break, resulting in lower reliability. Therefore, it is of practical importance to increase the mechanical strength of porcelain as much as possible. By the way, Pb(Mg _1/2 W _1/2 ) O ₃ -PbTiO ₃ based ceramic composition has already been published in N. N. Krajnik, A. Ai. Maglanovskaya NNKrainik
and AIAgrarovskaya (Fiziko Tverdogo
Tela, Vo.2.No.1, pp70-72.Janvara1960), and (SrxPb _1-x TiO ₃ ) _a
(PbMg _0.5 W _{0.5 O 3 )} b [However, x=0 to 0.10,
a is 0.35-0.5, b is 0.5-0.65, and a
+b=1] is also disclosed in JP-A-52-21662 as a monolithic capacitor and its manufacturing method, and also as a dielectric powder composition in JP-A-52-21699. However, none of them disclose any specific resistance, and the practicality of these ceramic compositions was not clear. In addition, the inventors have already found that Pb (Mg _1/2 W _1/2 ) O ₃ can be sintered at temperatures of 910-950 °C.
It consists of a two-component system of _PbTiO3 , which is
We propose a composition in which, when expressed as (Mg _1/2 W _1/2 )O ₃ ] _X [PbTiO ₃ ] _1-X , X is in the range of 0.65<X≦1.00. This composition has a high product of dielectric constant and specific resistance, and has excellent electrical properties with low dielectric loss. However, since all of the above compositions have low mechanical strength, their applications have had to be limited to a narrow range. Regarding the ternary system including the Pb(Mg _1/2 W _1/2 )O ₃ -PbTiO ₃ system, Japanese Patent Application Laid-open No. 111011/1983 describes the Pb(Mg _1/2 W _1/2 )O ₃ -PbTiO ₃ system. -Pb
(Mg _1/3 Nb _2/3 ) O ₃ system was changed to Pb (Mg _1/2 W _1/2 ) O ₃ ―PbTiO ₃ ―Pb in JP-A-55-117809.
(Mg _1/3 Ta _2/3 )O ₃ systems are disclosed respectively. However, none of them discloses specific resistance or mechanical strength, and the practicality of these ceramic compositions was not clear. In addition, the present inventors have already discovered that Pd (Mg _1/2 W _1/2 )
A ternary composition of O3 _- PbTiO3 _- Pb(Ni1 _/ 3Nb2 _/3 ) _O3 has already been proposed. This composition contains 900~
It can be sintered at a low temperature of 1050°C, and has excellent properties such as high dielectric constant, low dielectric loss, and high insulation resistance at room temperature and high temperature. However, since this composition has low mechanical strength, its use has had to be limited to a narrow range. In view of the above points, the present invention provides temperature control of 900 to 1050℃.
A highly reliable porcelain composition that can be sintered in the low-temperature region of Magnesium lead tungstate [Pb (Mg _1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and lead nickel niobate [Pb
A three-component composition consisting of (Ni _1/3 Nb _2/3 ) O _{3 ]} [Pb (Mg _1/2 W _1/2 ) O ₃ ] _X [PbTiO ₃ ] _y [Pb
(Ni _1/3 Nb _2/3 )O ₃ ] _z (where x+y+z=1.00) In this three-component composition diagram, the following composition point (x=0.693, y=0.297, z=0.01) ( x=0.495, y=0.495, z=0.01) (x=0.195, y=0.455, z=0.35) (x=0.10, y=0.40, z=0.50) (x=0.06, y=0.24, z=0.70 ) and in the composition range surrounded by these five points, add manganese lead tantalate [Pb (Mn _1/3 Ta _2/3 ) O ₃ ] as a main component as a subcomponent. On the other hand, it is characterized by containing 0.05 to 8 mol%. The present invention will be explained in detail below with reference to Examples. Lead oxide (PbO), magnesium oxide (MgO), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), nickel oxide (NiO) and niobium oxide (Nb ₂ O ₅ ), oxidized as starting materials with a purity of 99.9% or higher. Tantalum (Ta ₂ O ₅ ) and manganese carbonate (MnCO ₃ ) are used, and each is weighed so as to achieve the mixing ratio shown in the table. Next, the weighed materials were wet-mixed in a ball mill, preheated at 750-800°C, and this powder was ground in a ball mill, divided into pieces, dried, and an organic binder was added to the powder, which was sized and pressed.
We created four disks with a diameter of 16 mm and a thickness of approximately 2 mm, and a cylinder with a diameter of 16 mm and a thickness of approximately 10 mm. Samples having the composition range of the present invention were then sintered in air at a temperature of 900-1050°C for 1 hour. Silver electrodes were baked on the top and bottom surfaces of four sintered disks at 600℃, and the frequency was 1K using a digital LCR meter.
The capacitance and dielectric loss were measured at Hz, voltage 1V _r.n.s and _temperature 20°C, and the _dielectric constant was calculated. Next, use a super insulation resistance meter
Apply a voltage of 50V for 1 minute to measure the insulation resistance at a temperature of 20
℃ and 125℃, and the specific resistance was calculated. In order to evaluate the mechanical properties in terms of bending strength, 10 rectangular plates with a thickness of 0.5 mm, a width of 2 mm, and a length of about 13 mm were cut out from the sintered cylinder. The distance between the fulcrums was set to 9 mm, and the breaking load Pm [Kg] was measured using the two-point method, and τ =
The bending strength τ=[Kg/cm ² ] was determined according to the formula 3/2Pml/Wt ² [Kg/cm ² ]. However, l is the distance between the fulcrums,
t is the thickness of the sample, and W is the width of the sample. The electrical properties were determined from the average value of 4 disk samples, and the bending strength was determined from the average value of 10 rectangular plate samples. The main component of the porcelain obtained in this way [Pb (Mg _1/2 W _1/2 ) O ₃ ] _x
[PbTiO ₃ ] _y [Pb(Ni _1/3 Nb _2/3 ) O ₃ ] _z compounding ratio x, y, z and amount of subcomponents added, dielectric constant, dielectric loss, resistivity at 20℃ and 125℃, The relationship between flexural strength and bending strength is shown in the table below.

【table】

[Table] As is clear from the results shown in the table, Pb
(Mg _1/2 W _1/2 )O ₃ −PbTiO ₃ −Pb
A composition within the scope of the present invention in which Pb(Mn _1/3 Ta _2/3 ) O ₃ is added as an accessory component to a (Ni _1/3 Nb _2/3 ) O ₃ ternary composition has a dielectric constant. is 3090~13510
It has a high dielectric loss of 0.3 to 3.1%, and a high specific resistance of 3.5×10 ¹² to 2.1×10 ¹³ Ω・cm at 20°C, and 7.5×10 ¹⁰ to 3.8×10 ¹² even at 125°C.
It shows a high value of Ω・cm, and also has a high bending strength.
It can be seen that it is a highly reliable and extremely practical porcelain composition that exhibits a value of 980 to 1410 Kg/cm ² , which is sufficiently high for practical use. The porcelain of the present invention, which exhibits these excellent properties, has a sintering temperature of 1050°C or lower, so
In addition to being able to reduce the cost of the internal electrodes of multilayer capacitors, this also has the extremely excellent effect of saving energy and furnace materials. Note that the main component composition of the present invention is [Pb
(Mg _1/2 W _1/2 )O ₃ 〕 _x 〔PbTiO ₃ 〕 _y 〔Pb
(Ni _1/3 Nb _2/3 )O ₃ ] When expressed as _z (where x+y+z=1.00), its composition is the point (x=0.693, y=0.297, z=0.01) in the three-component composition diagram (x =0.495, y=0.495, z=0.01) (x=0.195, y=0.455, z=0.35) (x=0.10, y=0.40, z=0.50) (x=0.06, y=0.24, z=0.70) The content of the subcomponent added is limited to 0.05 to 8 mol% relative to the main component. In the three-component composition diagram showing the main component composition range, the resistivity at high temperatures becomes small outside the line connecting composition points 2 and 6 and composition points 17 and 19, making it impractical. Outside the line connecting composition points 6, 13, and 17, the Curie point deviates significantly toward higher temperatures than the practical range, so the dielectric constant decreases; outside the line connecting composition points 19 and 2,
Since the Kyrie point is significantly shifted to the lower temperature side than the practical range, the dielectric constant becomes small, making it impractical. Furthermore, if the amount of Pb (Mn _1/3 Ta _2/3 ) O ₃ added, which is a subcomponent, is less than 0.05 mol%, the effect of improving the bending strength will be small, and if it exceeds 8 mol%, the bending strength will decrease. Not practical. The figure shows the composition range of the main components of the present invention. The numbers shown in the figure correspond to the numbers of the main component blending ratios shown in the table.

[Brief explanation of the drawing]

The figure is a diagram showing the main component composition range of the present invention and the composition points shown in Examples.

Claims (1)

[Claims] 1. Magnesium lead tungstate [Pb
(Mg _1/2 W _1/2 )O ₃ ], lead titanate [PbTiO ₃ ] and lead nickel niobate [Pb(Ni _1/3 Nb _2/3 )
A _three -component composition consisting of [Pb
(Mg _1/2 W _1/2 )O ₃ 〕 _x 〔PbTiO ₃ 〕 _y 〔Pb
(Ni _1/3 Nb _2/3 ) O ₃ ] When expressed as _z (however, x+y+z=1.00), in this three-component composition diagram,
The following composition points (x=0.693, y=0.297, z=0.01) (x=0.495, y=0.495, z=0.01) (x=0.195, y=0.455, z=0.35) (x=0.10, y= 0.40, z = 0.50) (x = 0.06, y = 0.24, z = 0.70) and in the composition range surrounded by these five points, manganese lead tantalate [Pb ( A porcelain composition characterized in that it contains Mn _1/3 Ta _2/3 ) O ₃ in an amount of 0.05 to 8 mol % based on the main component.