JPH01172256A - Raw power for producing easy-to-sinter lead - Google Patents

Abstract

PURPOSE:To obtain the title raw powder capable of easily providing a high- density sintered compact by low-temp. calcination and having excellent degree of sintering and reactivity by mixing lead (compd.) powder into the partial solid soln. powder of a specified lead-contg. oxide. CONSTITUTION:The powdery compds. (e.g., PbO, SrCO3, and TiO2) in the amts. corresponding to the components of a desired material are mixed on a dry or wet basis, the mixture is calcined at 600-1,000 deg.C to conduct a solid-phase reaction to obtain the partial solid soln. powder of a lead-contg. oxide shown by the formula [A is a bivalent metal element or >=2 kinds of metal elements wherein the mean valency is controlled to two, B is a tetravalent metal element or >=2 kinds of metal elements wherein the mean valency is controlled to four, (x) is 0.9-1.0, (y) is 0.8-1.0, and (z) is 0.9-1.1]. The powder is disintegrated and classified, as required, lead powder or powdery lead compds. such as PbO and PbCO3 are added to the extent of 0.1-25atom.%, and the powder is uniformly mixed on a wet basis preferably by using a highly volatile liq. (e.g., acetone).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a raw material powder for producing an easily sinterable lead-containing oxide.

[Conventional technology and its problems]

Sintered bodies of lead-containing oxides, especially perovskite phase (structure)
The sintered body of lead-containing oxide with
Many of them are useful as dielectric materials. Therefore, from the standpoint of industrial production of these useful materials, there is a strong demand for powder raw materials for producing lead-containing oxides that are easily sinterable and can be sintered at low temperatures and yield sintered bodies with high density.

Conventional raw material powders for producing lead-containing oxides form a solid solution, and the production method involves converting compound powders such as oxides and carbonates containing various metals that should constitute lead-containing oxides into desired compositions. There is a so-called solid-phase method in which a mixture is weighed and a solid-phase reaction is performed by calcination.

However, the powder thus obtained has a drawback of low reactivity, making it difficult to obtain a high-density sintered body.

On the other hand, it is known that the firing temperature can be lowered by adding Pbo, the main component of the base material, as a liquid phase agent to lead-based ceramic materials in excess of the stoichiometric composition (Osamu Yamaguchi, "Powder and Powder Metallurgy, Vol. 17, No. 3, p. 116, 1970). However, in such a method, Pb
Since the amount greatly exceeds the stoichiometric amount, there is a risk that the electrical properties may change or that solid solution formation may become insufficient.

An object of the present invention is to provide an easily sinterable raw material powder for producing a lead-containing oxide that does not have such drawbacks and can be made into a sintered body with a particularly high sintered density by low-temperature firing.

(Means for Solving the Problems) As a result of intensive studies in order to achieve the above object, the present inventors have developed a mixture of a partial solid solution and a compound mainly containing lead, rather than a solid solution powder as in the past. It was discovered that a sintered body that is easy to sinter and has a particularly high sintered density can be produced by using a completely new constituent powder that has never been seen before, and the present invention was achieved based on this discovery.

That is, the present invention provides powder of a partial solid solution represented by the formula (PbXA+-x)yB*Os, with a concentration of 0.1 to 25
This is a raw material powder for producing easily sinterable lead-containing oxides, which is made by mixing atomic % of lead powder or lead compound powder.

(However, Pb is lead, and A is a metal element with a divalent valence or 2 contained in a ratio such that the average valence is divalent.)
B is a metal element with oxygen hexacoordination and a valence of 4, or 2 or more metal elements contained in a ratio such that the average valence is 4; is oxygen,
X is 0.9 to 1.0, y is 0.8 or more and less than 1.0, and 2 is 0.9 to 1.1. ) The present invention will be further explained in detail below. The lead-containing oxide of the present invention is, for example, PbZr0+
PbTiOi solid solution or this solid solution contains Pb(B"1/3 B"2/3)03, Pb(n"1/
2 B"1/2) 03, Pb(B"1/2 B"1/2
)03, Pb(B"2/3 B"1/3)03, Pb(
B"1/4 B"3/4) 01, (However, B":
Lis Cu, B”: Mgs Ni, ZnsM
n, Co, 5n1Fe, Cd, B”: Mn
, sb, AI Yb.

In, Fe, Go, Se, Y: B”: N
b5Sb, Ta, Bi.

B”: W, Te, Re) or some of the above Pb is added with Sr.

These include those substituted with Ba, Ca, La, etc.

The term "partial solid solution" means that the component compounds are not simply a mixture, but at least a portion thereof forms a solid solution. A is a divalent metal element such as Sr, or two or more metal elements contained in a ratio such that the average valence is divalent. The ratio of Pb and A is such that the atomic ratio X of Pb is 0.9 to 1.
．． Must be 0.

When X is less than 0.9 or exceeds 1.0, the effect of improving sinterability is reduced. The atomic ratio y of the total amount of Pb and A is 0.8
It must be greater than or equal to 1.0. When y is less than 0.8, the solid solution of the partial solid solution is insufficient, and the solid solution is likely to be insufficient when producing an oxide sintered body using the raw material powder of the present invention, resulting in a decrease in properties. When y becomes 1.0 or more, the effect of improving sinterability decreases.

The partial solid solution oxide powder is preferably one in which various metal components as constituent components are uniformly distributed, and the powder characteristics are preferably small in particle size and narrow in particle size distribution.

In order to specifically explain the partial solid solution oxide powder, an example of its manufacturing method will be described below. After thoroughly mixing the compound powders of each component, they are calcined to cause a solid phase reaction. Compound powders for each component include inorganic compounds such as metal oxides, carbonates, basic carbonates, nitrates, and hydroxides, organic acid salts such as oxalates and formates, or mixed crystals thereof. . These metals or metal compounds are preferably those that do not leave behind impurities such as halogens such as chlorine, ions, phosphorous, etc. after calcination. Specific examples include PbO, Pbff04, Pb(OH), , PbC
0,, Pb5CO+(OH)z, 5rCOs, 5r
(CHzCOO)z ・54u, o, Sr (NO3
)! , 5r(OH)z ・81hO1SrO5Ca
CO,, Ca(OH)z, CaOSBa(CHsCO
O)g, BaC0z, Ba(HCOO)z, Ha
(OR)z ” 8HtO1BaCzOn ・HzO
lBaO, BaC1z, Bang, Mg, Mg(O
H)z, MgCzOn ・2820, Mgα, Mn(
C8: +C00)z ・4HzO1MnCO3, Mn
(IICOO) z ・21120, Mn (NO
3) z, Mn, Zn, ZnO1Zn(CHsCO
O)z ・2HzO1NiSNi(CH3COO)z
・41hO1NiCO, ・2Ni (011) z
・4H20, N i (HCOO) z ・2■20
, NiO, Ni2O+ , Co, Co(CH+C0
0)z ・4HtO1CoO.

Y, Y, 0. +, In, InzO*, Nb
S NbzOs, Ta,, TazOs, A2,
Affi 203, An (OH)3, F
e, FeCzO4' 28zO1Fez03, Fe2O
4. In addition to simple metals and metal compounds such as Zr, ZrOz, Ti, and TiO2, compounds consisting of two or more metals,
Examples include solid solutions. Note that these powders are preferably fine powders with good mixability and dispersibility.

As for the mixing method, general methods such as using a mortar or ball mill may be used, and in particular water, alcohol,
Wet mixing using a liquid such as acetone or chlorocene, particularly a highly volatile liquid, is more efficient and preferable.

Note that the material of the device used for mixing is preferably an organic material such as nylon since it is difficult for metal impurities to enter, and a ball mill using zirconia balls is also preferred. In addition, if the composition is such that aluminum impurities are not a problem, alumina may be used.

The calcination temperature varies depending on the composition of the mixture, and is particularly related to the shrinkage start temperature and diffusion coefficient of the mixture, but it is
-1000°C1, preferably 700-900''C1, more preferably 720-880°C.

At temperatures lower than 600'C, the efficiency of the reaction is low and the solid phase reaction of the mixed powder becomes insufficient. Moreover, when the temperature exceeds 1000°C, agglomerated powder tends to be formed, and the particle size of the partially solid solution powder becomes irregular. When the particle size of the partially solid solution powder becomes irregular, the reactivity of the obtained raw material powder for producing lead-containing oxides decreases,
The sintering start temperature must be high, which is undesirable because the sintered density becomes high.

Calcination may be performed in a normal electric furnace or the like. When the oxide powder contains lead, in order to prevent lead from evaporating, it is preferable to carry out the process in a sealed state or in a lead atmosphere.

Further, the partially solid solution powder obtained by calcining may be further crushed or classified. The crushing may be carried out by a conventional method using a mortar, a ball mill, a jet mill, etc., and wet crushing using water or the like is particularly preferable to dry crushing. It is preferable to improve the uniformity of the particle size of the powder by crushing in order to improve the sintered density.

Next, lead powder or lead compound powder is Pb, Pbo,
Pb+On, Pb(OH)z, PbC0:+, P
It is a powder such as b3COs(OH)z, especially Pb,
O4 powder is preferred. The mixed amount of these powders must be 0.1 to 25 at % of the oxide powder of the partial solid solution. If it is less than 0.1 atomic %, the improvement in reactivity during sintering will be insufficient, and if it exceeds 25 atomic %, the sintered body may be deformed or its electrical properties may change, which is not preferable.

Component B is a metal element such as Ti or Zr which has oxygen hexacoordination and has a valence of 4, or two or more metal elements contained in a ratio such that the average valence is 4. Z is 0.9 to 1.1. If 2 is less than 0.9 or more than 1.1, the solid solution of the oxide powder tends to be insufficient, and the properties deteriorate.

Incidentally, lead powder or lead compound powder may be mixed with the partial solid solution oxide powder, and powder of a component including component A or component B may be mixed as necessary. The total amount of lead or lead compounds, that is, the total amount of lead in the raw material powder for producing an easily sinterable lead-containing oxide, is preferably in a range from a stoichiometric amount to an excess of 5 atomic %. If the lead content exceeds 5 atomic %, electrical properties such as withstand voltage will deteriorate, which is undesirable.

Although the present invention is a mixture of a partial solid solution powder and the above-mentioned compound powder, it is important that the mixed state is uniform. An analytical means such as an X-ray microanalyzer is used to evaluate the mixing state, and it is preferable that the mixing state be uniform at least on the order of microns. In addition, as a mixing method to achieve such a mixed state, general methods such as using a mortar or ball mill may be used, and in particular, it is preferable to use liquids such as water, alcohol, acetone, chlorocene, etc., especially highly volatile liquids, rather than dry mixing. Wet mixing is more efficient and preferable.

The raw material powder for producing easily sinterable lead-containing oxides of the present invention is generally used for producing sintered bodies.

The sintered body may be produced by any conventional method. That is, it is a method of molding by pressure molding, sheet molding, etc. and sintering at a temperature of 900 to 1300°C, although it varies depending on the composition.

EXAMPLES The present invention will be further specifically explained below with reference to Examples.

Examples 1 to 7, Comparative Example 1 First, Pbx (Mgl/3 Nb2/3)o, +s
A partial solid solution powder represented by the formula Zro, ao Tio, 4s was produced. The value of X is as shown in Table 1.

That is, first, PbOlMgO calculated from the above formula
, Nb, 0. , TiO2 and ZrOt reagent powders were mixed in a ball mill for 12 hours, and then the mixed powder was heated to a temperature of 8.
Calcining was performed at 00 to 850°C for 1 hour. When the obtained partially solid solution powder was evaluated by powder X-ray diffraction, there was a peak of perovskite solid solution phase, and it was confirmed that the powder was partially dissolved in solid solution. Next, Pb3 is added to the obtained partially solid solution powder.
0. A 1.00-x equivalent amount of powder (special grade reagent) was added and mixed in a ball mill for 24 hours. Comparative Example 1 did not include Pb3O4 powder.

In order to evaluate the obtained raw material powder of the present invention, a molding pressure of 1
000 kg/cXa T: A disk with a diameter of 20III11 was press-formed and sintered for 3 hours at the sintering temperature shown in Table 1. Table 1 shows the results of the sintered density. The results in Table 1 show that the raw material powder of the present invention is sintered with high density at low temperatures.

Table 1 Examples 8 to 11, Comparative Example 2 First, Pbx (Mgl/3 Nb2/3)o, +s
Partial solid solution oxide powders represented by the formulas Zro, aoTio, and ash3 were produced in the same manner as in Examples 1 to 7. The values of X are as shown in Table 2. Next, Pb3O4 powder (reagent special grade) was added in the amount shown in Table 2 to the obtained partial solid solution powder, and the mixture was mixed in a ball mill for 24 hours. Sintering was performed under the same conditions as Examples 1 to 7, and the sintered density was measured. These results are shown in Table 2. In addition,
The sintered body of Example 11 was fused. From the results in Table 2, it can be seen that the raw material powder of the present invention is sintered with high density at low temperatures.

Examples 12-18, Comparative Examples 3-9 First, a partial solid solution powder represented by the formula in Table 3 was produced.

That is, first, PbO, NiO calculated from the above formula
, 5bzO+, Ta205, WOz, ZnO.

SrCO3, CoO, MgO-, Nb2O5, TxOz
Partial solid solution powders were produced from reagent powders of ZrO and ZrO in the same manner as in Examples 1 to 7. In the case of Examples 12 to 18, Pb! is added to the partially solid solution powder obtained next. 04 powder (special grade reagent) was added in the amount shown in Table 3 and mixed in a ball mill for 24 hours. In the case of Comparative Examples 3 to 9, Pb30.0 was not added. Sintering was performed under the same conditions as Examples 1 to 7, and the sintered density was measured. These results are shown in Table 3. The results in Table 3 show that the raw material powder of the present invention is sintered with high density at low temperatures.

〔Effect of the invention〕

Claims (1)

[Claims] 0.1 to 25 atomic % of the partial solid solution powder represented by the formula (Pb_xA_1_-_x)_yB_zO_3
A raw material powder for producing easily sinterable lead-containing oxides made by mixing lead powder or lead compound powder. (However, Pb is lead, and A is a metal element with a divalent valence or 2 contained in a ratio such that the average valence is divalent.)
B is a metal element with oxygen hexacoordination and a valence of 4, or 2 or more metal elements contained in a ratio such that the average valence is 4; is oxygen,
x is 0.9 to 1.0, y is 0.8 or more and less than 1.0, and z is 0.9 to 1.1. )