CN103288437B - Six-layer ferrotitanium yttrium bismuth cobaltate ceramic material with multiferroic performance and preparation method thereof - Google Patents

Abstract

The invention relates to a six-layer ferrotitanium yttrium bismuth cobaltate ceramic material with multiferroic performance and a preparation method thereof. The Aurivillius-type oxide ceramic with a chemical formula Bi6YFe2CoTi3O21 has good ferroelectricity and ferromagnetism over room temperature. A Bi6YFe2CoTi3O21 sample is prepared by an improved Pechini method, and the Fe-O and Co-O octahedrons are orderly arranged relatively so as to locally obtain coupling between Fe-O-Co and Y-O-Co/Fe to improve the ferroelectric and magnetic performance of the sample. The technology is simple, reasonable and efficient, the sample preparation temperature is far lower than the preparation temperature of the prior art, and the technology is environment-friendly and very convenient for industrial production.

Description

Six-layer structure yttrium bismuth titanate cobaltate ceramic material with multiferroic properties and preparation method thereof

technical field

The invention relates to the field of multiferroic oxide ceramic materials, and more specifically relates to a six-layer structure yttrium bismuth titanate cobaltate ceramic material with multiferroic properties and a preparation method thereof.

Background technique

Magnetoelectric multiferroic materials refer to materials that exhibit ferroelectric order and ferromagnetic/antiferromagnetic order at the same time in a certain temperature range, and there is a certain coupling between them. Recently, this material has attracted more and more attention. On the one hand, it can not only be used in the research and development of ferroelectric and magnetic devices, but more importantly, it can use the coupling between magnetoelectricity to provide additional advantages for the design and application of devices. One degree of freedom, thus showing extremely attractive application prospects in emerging spintronics, multi-state information storage, electrically driven ferromagnetic resonators, and magnetically regulated piezoelectric sensors. So far, among the multiferroic materials discovered so far, only BiFeO ₃ with ABO ₃ type structure has ferroelectricity and ferromagnetism above room temperature, but the leakage current of the sample is large and the properties such as antiferromagnetism above room temperature cannot meet the requirements. practical application needs. In recent years, extensive research has been carried out on BiFeO ₃ samples, and the results show that the electrical properties of the samples may be improved by the method of A-site doping, the leakage current of the samples can be reduced, and the ferroelectric properties of the samples have also been significantly improved. Since BiFeO ₃ is antiferromagnetic at room temperature, and antiferromagnetism is not sensitive enough to the applied magnetic field, there is no report on the practical application of BiFeO ₃ materials with a single phase structure.

In order to meet the needs of multiferroic materials in practical applications, multiferroelectric materials have become one of the hotspots in materials science research in recent years. One of the main research directions of multiferroelectric materials at present is to study materials with a single structure, in which double perovskite materials have been widely paid attention to. In the research, it was found that coupling two kinds of magnetic ions with d ⁰ electronic structure at the B site of the sample can greatly improve the ferromagnetic properties of the sample, but there are still two main problems in the research of double perovskite materials: ( 1) The sample synthesis must be prepared under high pressure, and it is difficult to ensure that the B-site ions of the sample have a good order; (2) The ferroelectric and ferromagnetic phase transition temperatures of the sample are not at the same time above room temperature. Aurivillius-type layered materials with perovskite-like properties have received extensive attention in recent years due to their unique crystal structure and properties. The structural formula of the Aurivillius type layered multiferroic material can be written as: Bi ₂ A _m-1 B _m O _3m+3 , specifically the system of the present invention is Bi ₂ Bi _m+2 Fe _m Ti ₃ O _3m+12 , or written as Bi ₂ O ₂ +Bi ₄ Ti ₃ O ₁₂ (BTO)+nBiMO ₃ (n=1, 2..., M is a magnetic ion), that is, the material can be regarded as a three-layer ferroelectric with a perovskite structure The material BTO is combined with _the ionic group BiFeO ₃ with one or more magnetic units, _and its structure is that three titanium ^oxide (Ti-O ) octahedron and (Fe-O) octahedron with 1 or more magnetic units. Since the bismuth oxide layer functions as an insulating layer and a charge pool, it can effectively reduce the leakage current of the sample, which is of positive significance for improving the electrical properties of the sample.

Contents of the invention

In order to optimize the ferroelectric and ferromagnetic properties of Aurivillius-type layered ceramics, the present invention provides a six-layer structure yttrium-bismuth titanate-iron-cobaltate ceramic with multiferroic properties, the chemical formula of which is Bi ₆ YFe ₂ CoTi ₃ O ₂₁ .

The yttrium bismuth titanate cobaltate ceramic of the present invention has ferroelectricity and ferromagnetism at the same time above room temperature, and has small leakage current and considerable ferromagnetism, which provides the possibility for application in information storage, resonance, sensing and the like.

Another object of the present invention is to provide the preparation method of this Aurivillius type multiferroic oxide ceramics (six-layer structure titanic iron cobaltate yttrium bismuth ceramics with multiferroic properties), said method comprising:

Titanate (preferably n-butyl titanate (C ₁₆ H ₃₆ O ₄ Ti)), bismuth nitrate (preferably bismuth nitrate pentahydrate (Bi(NO ₃ ) ₃ ·5H ₂ O)), yttrium nitrate (preferably hexahydrate Yttrium nitrate (Y(NO ₃ ) ₃ 6H ₂ O)), iron nitrate (preferably iron nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O)), cobalt acetate (preferably cobalt acetate tetrahydrate (C ₄ H ₆ O ₄ Co·4H ₂ O)) according to stoichiometric ratio 3:6:1:2:1 dissolved in nitric acid solution, add complexing agent (preferably ethylenediaminetetraacetic acid (EDTA) and citric acid), EDTA, lemon The molar ratio of the acid to the metal ion is preferably 0.7:1:1; the solution is evaporated to dryness, and the obtained powder is calcined at 700-800°C for 2-4 hours to remove organic matter; Sintering at 1100°C for 5-10 hours to finally obtain the target product. In addition to muffle furnace sintering, hot pressing sintering can also be used in the method of the present invention.

The invention has a simple process and adopts the improved Pechini method to prepare Bi ₆ YFe ₂ CoTi ₃ O ₂₁ six-layer Aurivillius type multiferroic oxide ceramics, the structure of which is two bismuth oxide layers ((Bi ₂ O ₂ ) ²⁺ ). There are three titanium oxide (Ti-O) octahedrons, two iron oxide (Fe-O) octahedrons and one cobalt oxide (Co-O) octahedron sandwiched between them. Among them, the Bi ions at the A site are partially replaced by Y ions, which can effectively reduce the leakage current and improve the ferroelectric properties of the sample; two magnetic ions (M) Fe and Co with d ⁰ electronic structures are used as the B site ions, through Coupling improves the ferromagnetic properties of the sample.

The six-layer multiferroic oxide ceramic provided by the present invention has good ferroelectricity and ferromagnetism at room temperature. When the sample is measured at an electric field of 50kV/cm, the remanent polarization (2P _r ) is 0.88μC/cm ² . The coercive field (2E _c ) is 20kV/cm; the remanent magnetic susceptibility (2M _r ) of the sample is 1.48emu/g, and the coercive field (2H _c ) is 244Oe.

Description of drawings

Fig. 1 is the X-ray picture of sample in the embodiment of the present invention 1;

Fig. 2 is the scanning electron micrograph of sample in the embodiment of the present invention 1;

Fig. 3 is the transmission electron micrograph of sample in the embodiment of the present invention 1;

Fig. 4 is the ferroelectric performance measurement figure of sample in the embodiment of the present invention 1;

Fig. 5 is a measurement diagram of ferromagnetic properties of the sample in Example 1 of the present invention.

Specific implementation method

Example 1

Select chemically pure n-butyl titanate (C ₁₆ H ₃₆ O ₄ Ti), analytically pure bismuth nitrate pentahydrate (Bi(NO ₃ ) ₃ 5H ₂ O), high-purity (4N) yttrium nitrate hexahydrate (Y(NO ₃ ) ₃ 6H ₂ O), analytically pure ferric nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O), analytically pure cobalt acetate tetrahydrate (C ₄ H ₆ O ₄ Co 4H ₂ O) as raw materials, According to the stoichiometric ratio of 3:6:1:2:1, it is accurately weighed and dissolved in nitric acid solution, and ethylenediaminetetraacetic acid (EDTA) and citric acid are added as complexing agents, and the molar ratio of EDTA, citric acid and metal ions is 0.7 : 1: 1, stirring at a constant speed to form a clear solution.

Table 1 Preparation of Bi ₆ YFe ₂ CoTi ₃ O ₂₁

Drug Name molecular weight Drug purity Weighing mass/g C ₁₆ H ₃₆ O ₄ Ti 340.36 98% 7.893 Bi(NO ₃ ) ₃ 5H ₂ O 485.07 99% 22.4977 Y(NO ₃ ) ₃ 6H ₂ O 383.01 98% 2.9607 Fe(NO ₃ ) ₃ 9H ₂ O 404 98.5% 6.2459 C ₄ H ₆ CoO ₄ 4H ₂ O 249.08 99.5% 1.9254 EDTA 292.24 98% 20.5572

citric acid 210.14 98% 21.1171

Put the above-prepared solution in a crucible and evaporate it to dryness and burn it into powder; the obtained powder is pre-fired in a muffle furnace at 750°C for 3 hours to remove organic matter; the pre-fired powder is made into a cylinder under the condition of a pressure below 5Mpa The body sample, the sample size is φ12mm×2mm; after tablet molding, it was sintered in a muffle furnace at 1000°C for 10 hours, and finally the target product was obtained.

Structural analysis of the sintered sample was carried out with an X-ray diffractometer (type D8 from Bruker Corporation of Japan), and Figure 1 was obtained. It can be seen from the figure that the sample is a ceramic sample with a single perovskite structure, and no second phase is found.

The morphology of the sample was observed with a scanning electron microscope (JSM-6510 type of Japan JEOL Company), and Figure 2 was obtained. It can be seen from the figure that the grain shapes of the samples are basically the same, the density of the samples is good, and no obvious voids appear.

The electron diffraction pattern of the sample was observed with a transmission electron microscope (model 2010 from Japan JEOL Company), and Figure 3 was obtained. It can be seen from the figure that the sample has a six-layer structure.

The ferroelectric properties of the samples at room temperature were measured with a ferroelectric property measuring instrument (Precision LC type, Radiant Technologies, USA), and FIG. 4 was obtained. It can be seen from the figure that at room temperature, the sample exhibits ferroelectricity. When the measured electric field is 50kV/cm, the remanent polarization (2P _r ) is 0.88μC/cm ² , and the coercive field (2E _c ) is 20kV/cm .

The magnetic properties of the sample at room temperature were measured with a vibrating sample magnetometer (EV7 type, ADE Company, USA), and Figure 5 was obtained. It can be seen from the figure that at room temperature, the sample shows ferromagnetism, the remanent magnetic susceptibility (2Mr) is 1.48emu/g, and the coercive field (2Hc) is 244Oe.

Example 2

Select chemically pure n-butyl titanate (C ₁₆ H ₃₆ O ₄ Ti), analytically pure bismuth nitrate pentahydrate (Bi(NO ₃ ) ₃ 5H ₂ O), high-purity (4N) yttrium nitrate hexahydrate (Y(NO ₃ ) ₃ 6H ₂ O), analytically pure ferric nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O), analytically pure cobalt acetate tetrahydrate (C ₄ H ₆ O ₄ Co 4H ₂ O) as raw materials, According to the stoichiometric ratio of 3:6:1:2:1, it is accurately weighed and dissolved in nitric acid solution, and ethylenediaminetetraacetic acid (EDTA) and citric acid are added as complexing agents, and the molar ratio of EDTA, citric acid and metal ions is 0.7 : 1: 1, stirring at a constant speed to form a clear solution.

Table 2 Preparation of Bi ₆ YFe ₂ CoTi ₃ O ₂₁

Drug Name molecular weight Drug purity Weighing mass/g

C ₁₆ H ₃₆ O ₄ Ti 340.36 98% 8.016 Bi(NO ₃ ) ₃ 5H ₂ O 485.07 99% 22.8483 Y(NO ₃ ) ₃ 6H ₂ O 383.01 98% 3.0068 Fe(NO ₃ ) ₃ 9H ₂ O 404 98.5% 6.3432 C ₄ H ₆ CoO ₄ 4H ₂ O 249.08 99.5% 1.9554 EDTA 292.24 98% 20.8776 citric acid 210.14 98% 21.5009

Put the above-prepared solution in a crucible and evaporate it to dryness and burn it into powder; the obtained powder is pre-fired in a muffle furnace at 700°C for 2 hours to remove organic matter; the pre-fired powder is made into a cylinder under the condition of a pressure below 5Mpa Body sample, the sample size is φ12mm×2mm; after tablet molding, it is sintered in a hot-press furnace at 900°C for 5 hours, and finally the target product is obtained.

The structure of the sintered sample was analyzed by X-ray diffractometer (D8 type of Japan Bruker Company), and the sample was a ceramic sample with a single perovskite structure, and no second phase was found.

The morphology of the samples was observed with a scanning electron microscope (JSM-6510 type of Japan JEOL Company), and the grain shapes of the samples were basically the same, the density of the samples was good, and no obvious voids appeared.

The electron diffraction pattern of the sample was observed with a transmission electron microscope (model 2010 from JEOL Corporation of Japan), and it was determined that the sample had a six-layer structure.

Measure the ferroelectric properties of the sample at normal temperature with a ferroelectric property measuring instrument (U.S. Radiant Technologies Corporation Precision LC type). At normal temperature, the sample shows ferroelectricity. _r ) is 0.92 μC/cm ² , and the coercive field (2E _c ) is 28 kV/cm.

Measure the magnetic properties of the sample at normal temperature with a vibrating sample magnetometer (EV7 type of American ADE Company). It is 216Oe.

Claims (5)

1. preparative chemistry formula is Bi ₆yFe ₂coTi ₃o ₂₁the method with six laminate structure ferrotianium cobalts acid yttrium bismuth potteries of multi-ferrum property, it is characterized in that comprising the following steps:

1) tetrabutyl titanate, five nitric hydrate bismuths, six nitric hydrate yttriums, Fe(NO3)39H2O, four acetate hydrate cobalts are stoichiometrically dissolved in salpeter solution at 3: 6: 1: 2: 1, and add complexing agent;

2) by solution evaporate to dryness, gained powder, at 700-800 DEG C of pre-burning 2-4 hour, removes organism;

3) at 800-1100 DEG C of sintering 5-10 hour, finally obtained target product after the powder compression molding of pre-burning,

Wherein said complexing agent is ethylenediamine tetraacetic acid (EDTA) and citric acid, and ethylenediamine tetraacetic acid (EDTA), citric acid and metal ion mol ratio are 0.7: 1: 1.

2., by method according to claim 1, it is characterized in that step 3) described in sintering be retort furnace sintering or hot pressed sintering.

3. a chemical formula is Bi ₆yFe ₂coTi ₃o ₂₁the six laminate structure ferrotianium cobalts acid yttrium bismuths potteries with multi-ferrum property, it is prepared in accordance with the method for claim 1.

4., by ferrotianium cobalt acid yttrium bismuth pottery according to claim 3, it is characterized in that structure is six layers of perovskite-like structure, namely at (Bi ₂o ₂) ²⁺3 Ti-O octahedrons, 2 Fe-O octahedrons and 1 Co-O octahedron is clipped between layer.

5., by ferrotianium cobalt acid yttrium bismuth pottery according to claim 3, it is characterized in that, in room temperature, there is ferroelectricity and ferromegnetism simultaneously.