TWI664146B - Dielectric ceramic material, method for manufacturing the same, dielectric composite material and uses thereof - Google Patents

Abstract

The invention provides a cerium oxide nickel ceramic powder prepared by an oxalic acid solvent method using ammonia water and ethylene glycol as a solvent. The powder is prepared by using different molar mixing ratios of nickel oxalate, cerium nitrate and cerium nitrate metal precursor, and is mixed with a resin to prepare a composite having a high dielectric constant. The composite made of La:Sr:Ni molar ratio of 1:3:1 contains 50 wt.% of ceramic powder, and has the highest dielectric constant of 112 and the lowest impedance characteristics. The contrast ratio of the fingerprint identification test reached 31, indicating that the yttrium nickel oxide ceramic composite prepared by the invention has high sensitivity to fingerprint recognition.

Description

Dielectric ceramic material, manufacturing method thereof, dielectric composite material and use thereof

The invention relates to a dielectric ceramic material, a method of fabricating a dielectric ceramic material, a dielectric composite material and a use of a dielectric composite material.

At present, the fingerprint identification sensor of the market can be composed of two types. One is a Fingerprint Sensor. The main purpose is to collect a complete fingerprint image, which can be either capacitive or optical. The other is Fingerprint Algorithm. After the fingerprint sensor of the current end collects the fingerprint image, the fingerprint image processing and fingerprint feature point extraction are performed by the algorithm. After the fingerprint template is generated, the original fingerprint image is discarded. Finally, the fingerprint image is discarded. Then perform fingerprint comparison. Among them, the capacitive sensor can be called a semiconductor wafer sensor, and has the advantages of thinning and miniaturization, and thus can be widely used in a handheld device.

Discussed by the package structure of the IC, the capacitive sensors currently used in mobile phones can be divided into three types: the first is to attach a sapphire material to the wafer, and to increase the capacitance signal by sapphire to improve the sensor. Sensitivity; the second is not to make the fingerprint sensor inside the IC, but to do it on the PCB; the third is to spray the high dielectric glue on the substrate, and then spray the hard coating on the upper surface. In order to prevent the sweat and acid and alkali of the fingers from eroding the surface of the wafer and achieving the effect of static electricity protection.

However, sapphire needs to use double-sided throwing, which consumes twice the capacity, and the sapphire substrate is so expensive that the sapphire substrate is sold at a higher price than the average mobile phone. Although the process of spraying the high dielectric adhesive on the substrate is relatively easy and low-cost, the multilayered materials are stacked together, causing the thickness of the dielectric layer to be too thick (50-100 μm), which in turn makes the fingerprint imaging effect worse.

Furthermore, regarding the high dielectric adhesive material, the preparation method of the nickel oxide-based ceramic dielectric material is mostly a solid-state reaction (SSR), and the solid state reaction method is to mix various types of oxide powders. After being together, it is prepared at high temperature and for a long time. Patent Document 1 proposes a method for producing Li _x Sc _0.02 Ni _0.98-x O by mixing a mixture of Li ₂ CO ₃ , Sc ₂ O ₃ and NiO with ethanol for 24 hours, and then calcining at 1000 ^o C for 10 hours; Patent Document 1 proposes a synthesis method of A _5/3 Sr _1/3 Ni _1-x Al _x O ₄ (A=La, Nd, x=0.2, 0.3), which is SrCO ₃ , La ₂ O ₃ and Al ₂ O ₃ in molar ratio of 2: 1: 1 ethanol was added and the zirconia balls using a ball mill for 24 hours and then fired at 1200 ^o C Xia for 3 hours.

[Technical Literature] Patent Document 1 Non-Patent Document 1 of US Patent No. 7616786 B2 Y. Liu, W. Wang, J. Huang, C. Zhu, C. Wang, Y. Cao, J. Mater. Sci.: Mater. Electron, 2014, 25, 1298-1302.

The present invention has been accomplished in view of the above prior art. The invention provides a method for manufacturing a dielectric ceramic material, which is different from the traditional solid state reaction method, and initially prepares a cerium oxide nickel by an oxalic acid solvent heating method, and then obtains a dielectric ceramic material by sintering.

In an embodiment of the present invention, a method for manufacturing a dielectric ceramic material includes: providing an aqueous ammonia solution containing cerium ions, cerium ions, and nickel ions; adding ethylene glycol to the aqueous ammonia solution to obtain a mixed solution; heating the The solution is mixed to form a precipitate in the mixed solution; the precipitate is dried; and the precipitate is obtained by firing the precipitate, wherein the dielectric ceramic material is an oxide mixture containing cerium, lanthanum and nickel.

Preferably, the method of manufacturing a dielectric ceramic material further comprises: when heating the mixed solution, the ethylene glycol is oxidized to form acetoxyacetic acid, and the acetoxyacetic acid forms a metal complex with the cerium ions and the cerium ions.

Preferably, the source of cerium ions is cerium nitrate; the source of cerium ions is cerium nitrate; and the source of nickel ions is nickel oxalate.

Preferably, the ratio of cerium ions, cerium ions and nickel ions in the mixed solution is La:Sr:Ni=1 to 5:1 to 5:1 to 3.

Preferably, the mixture solution was heated to reflux way, and the heating temperature is 120 ^o C ~ 180 ^o C.

Preferably, the reaction time for heating the mixed solution is from 1 to 7 hours.

Preferably, the temperature of the calcination is from 650 ^o C to 1300 ^o C.

The invention provides a dielectric ceramic material which is a ceramic dielectric material of yttrium nickel oxide.

In another embodiment of the present invention, the dielectric ceramic material is obtained by the above method, and includes: tetragonal Sr _0.5 La _1.5 NiO ₄ , hexagonal NiO, and hexagonal LaNiO ₃ .

The invention further provides a dielectric composite material. In still another embodiment of the invention, the dielectric composite material comprises: a resin and the dielectric ceramic material described above.

The invention further provides the use of a dielectric composite material, in another embodiment of the invention, the use of the above dielectric composite material for fingerprint identification.

According to the method for producing a dielectric ceramic material of the present invention, since the reaction temperature is lowered and the reaction time is shortened by the oxalic acid solvent heating method, the process time can be greatly shortened and the production efficiency can be improved. The obtained dielectric ceramic material may have both a tetragonal Sr _0.5 La _1.5 NiO ₄ , a hexagonal NiO, and a hexagonal LaNiO ₃ oxide. In addition, since the dielectric composite material prepared by mixing a dielectric ceramic material and a resin has a high dielectric constant and a low impedance, when a fingerprint sensor is sprayed on a substrate, the contact area can be increased without intervening. Good fingerprint imaging is still maintained when the thickness of the electric layer is maintained.

The method for producing a dielectric ceramic material of the present invention comprises: providing an aqueous ammonia solution containing cerium ions, cerium ions, and nickel ions; adding ethylene glycol to an aqueous ammonia solution to obtain a mixed solution; heating the mixed solution to form a precipitate in the mixed solution Drying the precipitate; and calcining the precipitate to obtain a dielectric ceramic material. Among them, the dielectric ceramic material is an oxide mixture containing cerium, lanthanum and nickel.

The configuration of the aqueous ammonia solution is exemplified by, but not limited to, dissolving nickel oxalate in aqueous ammonia and adding deionized water to a predetermined concentration, and dissolving the salt containing cerium and the salt containing cerium in deionized water, respectively, and then The three solutions are mixed together to obtain an aqueous ammonia solution containing cerium ions, cerium ions, and nickel ions.

As a metal precursor of the reaction, the source of nickel ions may be Nickel Oxalate (NiC ₂ O ₄ ). Nickel oxalate is substantially insoluble in water, but is soluble in aqueous ammonia to form nickel metal ions (Ni(NH ₃ ) ²⁺ ) and oxalate ions (C ₂ O ₄ ^2– ) as shown in formula (1). The source of cerium ions is not limited as long as it is soluble in water to produce cerium ions (La ³⁺ ), but it is preferred that the source of cerium ions be lanthanum nitrate (Lanthanum Nitrate, La(NO ₃ ) ₃ ); the dissolution formula of cerium nitrate dissolved in water is as shown in formula (2). The source of the cerium ion is not limited as long as it is a salt soluble in water to generate strontium ions (Sr ²⁺ ), but it is preferable that the cerium ion source is strontium nitrate (Sr(N ₃ ) ₂ ). The dissolution formula of cerium nitrate dissolved in water is as shown in formula (3). NiC2O4·2H2O + NH4OH → Ni(NH3)2+ + C2O42– + 2H2O (1) La(NO3)3·6H2O + H2O → La3+ + 3NO3‒ + 7H2O (2) Sr(NO3)2 + H2O → Sr2+ + 2NO3 ‒ + H2O (3)

The ratio of the metal precursor (cerium ion, cerium ion, and nickel ion) in the mixed solution may be La:Sr:Ni = 1 to 5:1 to 5:1 to 3.

Next, ethylene glycol is added to an aqueous ammonia solution containing cerium ions, cerium ions, and nickel ions to obtain a mixed solution, and the mixed solution is heated to cause a precipitate to be produced. The heating time can be from 1 to 7 hours.

The manner of heating is exemplified by, but not limited to, erecting a reflux tube to the opening of the reactor containing the mixed solution to reflux the volatilized ethylene glycol. The heating temperature can be from 120 ^o C to 180 ^o C. When the temperature reaches 120 ^o C, ethylene glycol (CH ₂ OHCH ₂ OH) is partially oxidized to produce acetaldehyde (CH ₃ CHO) as shown in formula (4). The acetaldehyde will continue to be oxidized and finally form acetoxyacetic acid (CH ₃ COOCH ₂ COOH) as shown in the formulas (5) to (8). The produced acetoxyacetic acid forms a complex with metal ions and precipitates in the presence of oxygen to form precipitates containing cerium, lanthanum and nickel. The precipitate formed by the above reaction was collected, and the precipitate was washed with deionized water to wash away the ethylene glycol, and then dried in an oven (for example, 60 ^o C). The dried precipitate is then calcined with a 650 ^o C high temperature furnace to obtain a dielectric ceramic material which is powdery and mainly contains Sr _0.5 La _1.5 NiO ₄ , La(OH) ₃ , NiO is as shown in formula (9). In addition, when La(OH) ₃ and NiO coexist, LaNiO ₃ can be further formed at a calcining temperature of 650 ^o C to 1300 ^o C, as in the formula (10). Preferably, when the calcination temperature is from 1000 ^o C to 1300 ^o C, a larger amount of LaNiO ₃ can be formed, and more preferably, when the calcination temperature is 1200 ^o C, the most content of LaNiO ₃ can be formed. Among the obtained products, Sr _0.5 La _1.5 NiO ₄ may preferably be a tetragonal system; NiO and LaNiO ₃ may be a hexagonal system.

 2CH2OHCH2OH + O2 → 2CH3CHO + 2H2O (4) 2CH3CHO + O2 → CH3COOH + 2H2O (5) CH3COOH + CH2OHCH2OH→ CH3COOCH2CH2OH + H2O (6) CH3COOCH2CH2OH+ O2 →CH3COOCH2CH2O+H2O (7) CH3COOCH2CH2O + O2 →CH3COOCH2COOH+ 2H2O (8) Ni ( NH3)2++ La3+ + Sr2+ + CH3COOCH2COOH + O2 → Sr0.5La1.5NiO4 +La(OH)3+NiO (9) Sr0.5La1.5NiO4 + La(OH)3+ NiO → Sr0.5La1.5NiO4 + LaNiO3 + NiO (10)

The above dielectric ceramic material can be further mixed with a resin to form a dielectric composite material (composite dielectric adhesive material), which can be used for coating on a fingerprint sensing wafer to improve capacitive fingerprint identification sensitivity.

(Example)

Hereinafter, the method for manufacturing the dielectric ceramic material (powder) of the present invention will be described by way of examples, and the dielectric ceramic material is further prepared into a dielectric composite adhesive material, and the dielectric composite adhesive material is applied to fingerprint identification. result. However, the embodiments are only intended to explain the spirit of the invention, and are not intended to limit the invention in any way, so that any modifications or changes relating to the invention in the spirit of the same invention are It should still be included in the scope of the invention as intended.

[Example 1]

--Preparation of dielectric ceramic materials (powder) --

First, 0.01 mole of nickel oxalate was dissolved in 10 ml of aqueous ammonia (NH ₄ OH), and deionized water was added to a 100 ml quantitative flask to prepare a 0.1 M nickel oxalate solution, followed by 100 ml of a 0.1 M cerium nitrate solution and 0.1 M cerium nitrate. 100 ml of the solution was mixed in an Erlenmeyer flask, and then 100 ml of ethylene glycol was added to obtain a mixed solution of La:Sr:Ni=1:1:1. After stirring on a hot stirrer before and heated to 180 ^o C, and then set up a reflux tube to the tapered bottle volatiles ethylene glycol at reflux the reaction is continued to produce a precipitate, continued to reflux for 6 hours. Finally, the precipitate is washed away with ethylene glycol several times with deionized water, then dried in an oven at 60 ^o C, and then simmered in a high temperature furnace at 1200 ^o C for 1 hour, so that it can be obtained. A dielectric ceramic material (powder) of nickel oxide. The dielectric ceramic material was identified by X-ray diffraction (XRD). Among them, the amounts of use of nickel oxalate, cerium nitrate and cerium nitrate (metal precursor) are shown in Table 2 in the form of molar ratio.

--Preparation of Dielectric Composite Adhesive --

The dielectric ceramic material is mixed with Liqin Industrial's RG-9823 and SK-7521 resin, and Hubei Xinjing New Material's UVR-6110 epoxy resin in a ratio of 1:1 (dielectric ceramic material is 50wt.%). . Further, an additive as shown in Table 1 is additionally added in a manner relative to the weight of the resin, the purpose of which is to uniformly disperse the powder of the dielectric ceramic material in the resin and to obtain a good workability coating of the obtained composite rubber. Sex. After the dielectric ceramic material is uniformly mixed in the resin, a dielectric composite rubber material can be obtained.

[Table 1]   Material Name Addition Ratio (wt.%) Curing Agent BI-7963 30.0 Flat Agent DC-56AD 0.3 Dispersant Triton X-45 2.0 Anti-settling Agent 4200-10 2.0 Metal Adhesive C-515.71HR 2.0 Leveling Agent Levaslip 407 1.0

--Preparation of dielectric test strips --

, On the glass sheet by screen printing 100μm coated with a layer of silver paste shown in FIG. 1, 150 ^o C by heat cured for 30 minutes to form a silver electrode as the lower electrode. The dielectric lamination adhesive material applied to a screen printing method on the lower electrode by 150 ^o C heat-cured to form a dielectric layer 30 min. Finally, on the cured dielectric layer by screen printing of silver coated plastic 6mm × 6mm through 150 ^o C 30 minutes to form a silver electrode as the upper electrode, a flat plate structure, for use in subsequent measuring dielectric properties.

[Embodiment 2]

A dielectric ceramic material and a dielectric composite rubber containing an oxide of cerium, lanthanum and nickel were prepared in the same manner as in the first embodiment except that the amount of ammonia water was changed from 10 ml to 20 ml, and the amount of metal precursor used was molar ratio. Presented in Table 2.

[Table 2]   No. Metal precursor Mohr ratio NH4OH volume (ml) La Sr Ni Example 1 1 1 1 10 Example 2 20

[Examples 3 to 7]

A dielectric ceramic material and a dielectric composite rubber containing oxides of cerium, lanthanum and nickel were prepared in the same manner as in the first embodiment except that the reaction time was different by heating and refluxing, and the synthesis reaction time was shown in Table 3. .

[table 3]   No. Synthesis reaction time (hr) Example 1 6 Example 3 1 Example 4 2 Example 5 3 Example 6 4 Example 7 5 Example 8 7

[Examples 8 to 9]

A dielectric ceramic material and a dielectric composite rubber containing an oxide of cerium, lanthanum and nickel were prepared in the same manner as in the first embodiment except that the sinter temperature was different, and the sinter temperature was shown in Table 4.

[Table 4]   No. Ignition temperature (oC) Example 1 1200 Example 8 1000 Example 9 1300

[Examples 10 to 18]

A dielectric ceramic material and a dielectric composite rubber containing an oxide of cerium, lanthanum and nickel were prepared in the same manner as in the first embodiment except that the molar ratio of the metal precursor was different, and the molar ratio was shown in Table 5. .

[table 5]   Mole Ratio NH4OH Volume of Numbered Metal Precursor (ml) La Sr Ni Example 1 1 1 1 10 Example 2 20 Example 10 2 1 1 10 Example 11 3 Example 12 4 Example 13 5 Example 14 1 3 1 10 Embodiment 15 4 Embodiment 16 5 Embodiment 17 1 3 2 10 Embodiment 18 3

[Embodiment 19]

--Fingerprint Identification Measurement --

The dielectric composite adhesive material (dielectric ceramic material accounted for 50 wt.%) obtained in Example 14 was coated on a capacitive fingerprint sensing chip (product of force transmission company) by using a coating bar, as shown in FIG. 2 . Shown. After heat curing at 150 ^o C for 30 minutes, the fingerprint signal is taken and the system is analyzed. The verification system sensor is an imaging system mainly based on a tantalum nitride wafer and using a 32-bit Cortex M4 MCU verification system, and the finger is touched on the wafer to observe whether there is a clear contrast image. After the imaging is successful, the fingerprint input and recognition are continued.

[Examples 20 to 22]

The fingerprint identification measurement was performed in the same manner as in the embodiment 19 except that the dielectric ceramic material in the dielectric composite material occupies a different weight ratio as a whole, and the ratio thereof is shown in Table 6.

[Table 6]   Number Dielectric Ceramic Material (wt.%) Example 19 50 Example 20 0 Example 21 30 Example 22 70

(experimental results)

[Oxidation of ethylene glycol]

When the synthesis reaction temperature of 120 ^o C, the reaction solution was partially removed by gas chromatography mass spectrometry (GC-Mass) analysis. From the analysis chart of Fig. 3a, it is known that an acetaldehyde peak is generated when the analysis time is 2.9 minutes, indicating that the solvent ethylene glycol moiety is oxidized to produce acetaldehyde. A glycol peak was produced at 9.76 minutes of analysis, indicating that some of the ethylene glycol was not oxidized. In addition, in the electron ion mass spectrometry map of Fig. 3b, the results are compared with the main signals of acetaldehyde 44, 29 and the main signals of acetic acid 60, 45, 43 after comparison with the database. Therefore, the production of acetaldehyde can be confirmed.

[Composition of dielectric ceramic materials]

The reaction was refluxed resulting precipitate was dried and heated to 650 ^o C after 1 hour, XRD pattern of Figure 4 via confirmed: by oxalic acid, the solvent was synthesized by heating the precipitate to obtain 650 ^o C 1 hour to obtain a tetragonal (Tetragonal) structure of Sr _0.5 La _1.5 NiO ₄ (JCPDS 32-1241), Hexagonal La(OH) ₃ (JCPDS 36-1481) and Hexagonal NiO (JCPDS 44-1159). The LaNiO ₃ structure of the Hexagonal system is only present in a small amount in the dielectric ceramic material, so the XRD signal is not obvious.

[Effects of different ammonia concentrations on the dielectric constant of dielectric composites]

Nickel oxalate can be dissolved in ammonia water. Therefore, the effect of dissolving nickel oxalate in 10 ml and 20 ml of ammonia solution on the dielectric constant of dielectric composite rubber is discussed. The experimental results obtained in Examples 1 and 2 are shown in Fig. 5. The dielectric composite material prepared by powdering 10 ml of ammonia water and further prepared has a dielectric constant higher than that of ammonia water of 20 ml, and as shown in Fig. 6 As shown, the ammonia water of 10 ml results in a lower impedance. After the powder made by both calcination 1200 ^o C for 1 hour and the results of XRD pattern of the obtained 7, two sets of experiments were observed resulting powder rests Sr _0.5 La _1.5 NiO _4, NiO and Hexagonal The composition of LaNiO ₃ (JCPDS 33-0711). Among them, the powder made of 10 ml of ammonia water contains a relatively complete structure of LaNiO ₃ , which may be due to the fact that the dielectric composite rubber material has a high dielectric constant and a low electrical resistance.

[Effect of Different Synthesis Reaction Time on Dielectric Constant of Dielectric Composite Adhesives]

Since the powder made of 10 ml of ammonia water can be used to form a dielectric composite rubber material and has a high dielectric constant, nickel oxalate is fixedly dissolved in 10 ml of ammonia water, and the synthesis reaction is investigated by Example 1, Examples 3 to 8. The effect of time on the dielectric constant of the dielectric composite. The results of the dielectric constant of the powder and the resin obtained by different synthesis reaction times were as shown in FIG. When the powder synthesis reaction time in the dielectric composite adhesive material is increased from 1 hour to 6 hours, the dielectric constant of the dielectric composite rubber material increases, and the highest dielectric constant is obtained when the synthesis reaction time is 6 hours. . However, when the reaction time was increased to 7 hours, the dielectric constant of the dielectric composite rubber was lowered. This result is related to the structural form of the powder. After the powder is made different reaction times by burning Xia 1200 ^o C for 1 hour and its XRD results shown in Figure 9. The structure of the powder differs somewhat with different synthesis reaction times. When the synthesis reaction time is 1 to 2 hours, the structure of the powder simultaneously produces Sr _0.5 La _1.5 NiO ₄ , NiO and LaNiO ₃ structures. However, the (103) and (110) peaks of Sr _0.5 La _1.5 NiO ₄ did not appear. As the synthesis reaction time increases by 3 to 6 hours, both peaks appear in the Sr _0.5 La _1.5 NiO ₄ structure, and the (101) peak of LaNiO ₃ also appears in the structure. Therefore, the dielectric composite adhesive having a powder synthesis reaction time of 6 hours has a maximum dielectric constant. However, when the synthesis reaction time of the powder is 7 hours, the peaks of (101), (103), (110) and (220) of LaNiO ₃ are reduced, and the main components of the powder are Sr _0.5 La _1.5 NiO ₄ and NiO structure. This results in a decrease in the dielectric constant of the dielectric composite. From the above results, it was found that the best results were obtained when the synthesis reaction time of the powder was controlled to 6 hours.

[Effects of different calcination temperatures on the dielectric constant of dielectric composites]

According to the embodiment 1 and the examples 8 to 9, the powder prepared by the molar ratio of the metal precursor to La:Sr:Ni=1:1:1 is subjected to different calcination temperatures, and the powder particle size is the same as that of the crucible. As the temperature of the firing increases, a scanning electron microscope (SEM) image of 1000 ^o C, 1200 ^o C, and 1300 ^o C calcination temperature is sequentially shown in FIGS. 10a to 10c. The relationship between the different calcination temperatures and the dielectric constant of the dielectric composite adhesive is shown in FIG. When the calcination temperature of the powder was 1200 ^o C for 1 hour, the dielectric lamination adhesive sheet has the highest dielectric constant. The dielectric composite adhesive has a low dielectric constant after the powder is sintered at 1000 ^o C and 1300 ^o C. From the results of XRD in Fig. 12, it was found that after the powder was calcined at 1000 ^o C and 1300 ^o C, the LaNiO ₃ structure appeared only in a small amount in the powder, and the XRD signal was not obvious, resulting in the resulting dielectric composite adhesive. There is a lower dielectric constant.

[Effects of different proportions of ruthenium precursors on the dielectric constant of dielectric composites]

According to the first embodiment and the examples 10 to 13, the Sr:Ni=1:1 fixed ratio is added to the niobium precursor of different molar ratios, and the dielectric constant of the dielectric composite adhesive prepared by the powder is as shown in FIG. As shown, when the mixing ratio of the ruthenium precursor is 1, the dielectric composite of the obtained powder has a maximum dielectric constant. According to the XRD pattern of Fig. 15, the powder having a mixing ratio of ruthenium precursor of 1 contains a NiO structure, and an appropriate NiO content contributes to an improvement in dielectric constant. However, when the mixing ratio of the ruthenium precursor is increased to 2, the dielectric constant of the dielectric composite rubber is lower than that of the ruthenium precursor, and the peak of NiO of the powder becomes smaller in the XRD pattern. When the mixing ratio of the ruthenium precursor is continuously increased to 3 to 5, the dielectric composites of the three have a similar dielectric constant, whereas the dielectric constant of the dielectric composite has a lower dielectric constant of 2 than that of the ruthenium composite. . In addition, it was found in the XRD pattern that when the mixed molar ratio of the ruthenium precursor was 3 or more, the structure of the powder produced a higher proportion of cubic Cubic La ₂ O ₃ (JCPDS 22-0369). When the mixed molar ratio of the ruthenium precursor is 3 and 4, the structure of the powder produces a higher proportion of La(OH) ₃ structure. When the La mixed molar ratio is 5, the La(OH) ₃ structure of the powder disappears, but a higher proportion of Hexagonal La ₂ O ₃ (JCPD 05-0602) is produced. The grain size of the powder decreases as the amount of La ₂ O ₃ increases because most of the doped La ³⁺ ions precipitate from the normal grains and stay at the grain boundaries to subsequently limit the growth of the grains. So that its dielectric constant is lowered. From the above results, it was obtained that the powder was prepared from La:Sr:Ni=1:1:1, and the resulting dielectric composite adhesive material had the highest dielectric constant and low impedance.

In addition, as shown in FIG. 14a, from the results of the impedance analysis, when the mixing ratio of the ruthenium precursor is 1, the dielectric composite rubber has the lowest impedance, and when the mixing ratio of the ruthenium precursor is 2, the dielectric composite rubber The resistance increases. Further, as shown in Fig. 14b, when the mixing ratio of the ruthenium precursor is 3 or more, the dielectric composite rubber has a large electrical resistance.

[Effects of different proportions of ruthenium precursors on the dielectric constant of dielectric composites]

According to Example 1 and Examples 14 to 16, a different ratio of lanthanum precursor was added after a fixed ratio of La:Ni=1:1, and the dielectric constant of the dielectric composite rubber prepared by the powder is as shown in FIG. When the mixing ratio of the ruthenium precursor is 3, the dielectric constant of the prepared dielectric composite material has a maximum value. When the mixing ratio of the ruthenium precursor is increased to 4 to 5, the dielectric constant of the dielectric composite rubber material is lowered. This result shows that the dielectric constant of the dielectric composite material increases as the proportion of the ruthenium precursor increases, but when the ratio of the ruthenium precursor is too high, the dielectric constant decreases. It is mainly that if there is too much strontium content in the powder, a high disordered structure is generated, which affects the internal charge, resulting in a decrease in the dielectric constant of the dielectric composite adhesive. Further, as shown in Fig. 17a, when the mixing ratio of the ruthenium precursor is 1, the impedance of the dielectric composite rubber is larger than the impedance when the mixing ratio of the ruthenium precursor is 3. Further, as shown in Fig. 17b, if the mixing ratio of the ruthenium precursor is 4 or more, the dielectric composite adhesive material has a significant increase in impedance. Fig. 18 is an XRD pattern of a powder prepared by mixing ratios of different cerium precursors. When the mixing ratio of the cerium precursors is 1 and 3, the powder structure is LaNiO ₃ , and when the mixing ratio is 4 and 5, the powder is obtained. The LaNiO ₃ structure in the middle appears only in a small amount. Therefore, the LaNiO ₃ structure in the powder can make its dielectric composite rubber have a high dielectric constant and a low impedance.

[Effects of different proportions of nickel precursors on the dielectric constant of dielectric composites]

According to Example 14 and Examples 17 to 18, the La:Sr fixed mixed molar ratio of 1:3 was added with different proportions of nickel oxalate, and the dielectric constant of the dielectric composite adhesive prepared by the powder was as shown in FIG. Shown. When the molar ratio of the nickel precursor is 1, the prepared powder has the highest dielectric constant of the dielectric composite rubber. When the mixing ratio of nickel precursor is increased to 2 to 3, the dielectric constant of the dielectric composite rubber decreases, and the reason why the mixing ratio of nickel precursor affects the dielectric behavior may be attributed to the cause. to, nickel ions ionic radius (r ₆ ²⁺ = 0.74Å) is smaller than the ionic radius of lanthanum ions (r ₆ ²⁺ = 1.15Å) and strontium ions (r ₆ ²⁺ = 1.32Å) ion radius, nickel ions A displacement is generated to distort the crystal lattice. Another possible reason is that many defects (such as positive, negative, and neutral defects) are generated, resulting in a decrease in orientation polarization, which is generated on the surface and becomes disordered. In addition, an increase in oxygen vacancy defects also inhibits the movement and reversal of molecules. Further, as shown in FIG. 20, when the molar ratio of the nickel precursor is 1, the impedance of the dielectric composite rubber has a minimum value. When the molar ratio of the nickel precursor is 2 to 3, the impedance of the dielectric composite adhesive material is greatly increased. This result indicates that an increase in the proportion of nickel is disadvantageous for the improvement of dielectric properties and the reduction of impedance. However, it was found from the XRD pattern of the powder of Fig. 21 that when the mixing ratio of the nickel precursor was increased to 2 to 3, the LaNiO ₃ content in the powder was decreased, so that the XRD signal was not noticeable.

[Effect of Different Powder Contents on Fingerprint Identification in Dielectric Composite Adhesives]

According to Examples 19 to 22, powders made of different weight ratios of La:Sr:Ni=1:3:1 were mixed with a resin, and the dielectric constant of the dielectric composite rubber was as shown in Fig. 22, when the powder was As the weight ratio increases, the dielectric constant of the dielectric composite adhesive increases. The dielectric composite material prepared by this method has a dielectric constant of 112 at 1 MHz. The dielectric composite adhesive material is coated on the fingerprint identification wafer, and after heat curing, the fingerprint is collected by the system, and the result of the difference in the obtained ratio is shown in FIG. 23, wherein the dielectric composite adhesive material contains 50 wt. % of the powder has a higher rate of contrast. Although the dielectric composite rubber has a high dielectric constant of 70% wt., when the actual coating is applied to the wafer, the viscosity of the slurry is too large, which may cause surface unevenness. Therefore, the actual fingerprint identification The difference in the comparison rate has a lower result. In addition, the fingerprint identification of the powder of the dielectric composite rubber containing 50 wt.% of La:Sr:Ni = 1:3:1 and the dielectric composite adhesive containing 50 wt.% of BaTiO ₃ powder (commercial) Comparing the rate differences, the results obtained indicate that the powder prepared by the present invention can provide a high difference in fingerprint identification ratio. It is indicated that the dielectric composite adhesive material produced by the invention has high fingerprint recognition sensitivity.

According to the above experimental results, in the method for producing a dielectric ceramic material of the present invention, the heating temperature by the oxalic acid solvent heating method is only 120 ^o C to 180 ^o C, and the reaction time is 1 to 7 hours. Compared with the conventional method for preparing metal oxides using metal oxalates, it is still necessary to increase the temperature to 450 ^o C to 500 ^o C for 6 hours, and the reaction temperature required for synthesizing metal oxides of the present invention can be greatly reduced. . On the other hand, the metal oxide obtained by the oxalic acid solvent heating method of the present invention requires only one hour of calcination time to obtain a dielectric ceramic material composed of oxides of cerium, lanthanum and nickel. Therefore, the process time can be greatly shortened and the production efficiency can be improved.

Further, the obtained dielectric ceramic material may have both a tetragonal Sr _0.5 La _1.5 NiO ₄ , a hexagonal NiO, and a hexagonal LaNiO ₃ oxide. Due to the structure of the three oxides, the dielectric composite material prepared by mixing the dielectric ceramic material and the resin can have a high dielectric constant and a low impedance, and when it is sprayed on a substrate to produce a fingerprint sensor, Good fingerprint imaging can be maintained without increasing the contact area and thickness of the dielectric layer.

Fig. 1 is a structural view of a dielectric test piece for measuring a dielectric constant. 2 is a photograph of a dielectric composite material of the present invention applied to a capacitive fingerprint sensing wafer. Figure 3a is a GC-Mass analysis of the mixed solution. Figure 3b is a mixed solution of electron ion mass spectrum of FIG. 4 is a dielectric ceramic material is heated 650 ^o C for 1 hour XRD pattern. Figure 5 is a graph showing the dielectric constant of a dielectric composite material prepared using different aqueous ammonia volumes. Figure 6 is an impedance diagram of a dielectric composite material of a dielectric ceramic material prepared using different volumes of ammonia water. Figure 7 is an XRD pattern of a dielectric ceramic material prepared using different volumes of aqueous ammonia. Fig. 8 is a graph showing the dielectric constant of a dielectric composite material of a dielectric ceramic material prepared by different synthesis reaction times. Figure 9 is an XRD pattern of a dielectric ceramic material prepared by different synthesis reaction times. 10a to 10c are SEM images of dielectric ceramic materials prepared at different calcining temperatures. Figure 11 is a graph showing the dielectric constant of a dielectric composite material of a dielectric ceramic material prepared by different calcination temperatures. Figure 12 is an XRD pattern of a dielectric ceramic material prepared at different calcining temperatures. Figure 13 is a graph showing the dielectric constant of a dielectric composite material of a dielectric ceramic material prepared by different molar ratios. 14a and 14b are impedance diagrams of a dielectric composite material of a dielectric ceramic material prepared by different molar ratios. Figure 15 is an XRD pattern of a dielectric ceramic material prepared in different molar ratios. Figure 16 is a graph showing the dielectric constant of a dielectric composite material of a dielectric ceramic material prepared by different molar ratios. 17a and 17b are impedance diagrams of a dielectric composite material of a dielectric ceramic material prepared by different molar ratios. Figure 18 is an XRD pattern of a dielectric ceramic material prepared in different molar ratios. Figure 19 is a graph showing the dielectric constant of a dielectric composite material of a dielectric ceramic material prepared by different nickel molar ratios. Figure 20 is an impedance diagram of a dielectric composite material of a dielectric ceramic material prepared by different nickel molar ratios. Figure 21 is an XRD pattern of a dielectric ceramic material prepared by different nickel molar ratios. Figure 22 is a graph showing the dielectric constant of a dielectric composite material having different dielectric ceramic material contents. Figure 23 is a comparison of fingerprint identification of dielectric composites with different dielectric ceramic materials.

Claims (9)

A method for producing a dielectric ceramic material, comprising: providing an aqueous ammonia solution containing cerium ions, cerium ions, and nickel ions; adding ethylene glycol to the aqueous ammonia solution to obtain a mixed solution; heating the mixed solution in the mixed solution Forming a precipitate in a heating temperature of 120 ° C ~ 180 ° C; drying the precipitate; and calcining the precipitate to obtain the dielectric ceramic material, the calcining temperature is 1000 ° C ~ 1300 ° C, wherein the source of nickel ions It is nickel oxalate, and the dielectric ceramic material is an oxide mixture containing cerium, lanthanum and nickel. The method for producing a dielectric ceramic material according to claim 1, further comprising: when heating the mixed solution, the ethylene glycol is oxidized to form acetoxyacetic acid, and the acetophenoxyacetic acid and the cerium ion and cerium The ions form a metal complex. The method for producing a dielectric ceramic material according to claim 1, wherein the source of cerium ions is cerium nitrate; and the source of cerium ions is cerium nitrate. The method for producing a dielectric ceramic material according to claim 1, wherein the ratio of strontium ions, strontium ions, and nickel ions in the mixed solution is La:Sr:Ni=1~ 5:1~5:1~3. The method for producing a dielectric ceramic material according to claim 1, wherein the method of heating the mixed solution is a reflux method. The method for producing a dielectric ceramic material according to claim 1, wherein the time for heating the mixed solution is 1 to 7 hours. A dielectric ceramic material obtained by the method according to any one of claims 1 to 6, and comprising: a tetragonal Sr _0.5 La _1.5 NiO ₄ , a hexagonal NiO, and a hexagonal system. LaNiO ₃ . A dielectric composite material comprising: Resin and the dielectric ceramic material described in claim 7 of the patent application. The use of a dielectric composite material for applying the dielectric composite material according to claim 8 of the patent application to fingerprint identification.