JP4034139B2 - BiMnO3 crystal synthesis method and composition for BiMnO3 crystal synthesis - Google Patents

Description

【００４８】
図４に示すように、高圧域になるにしたがって、回折パターンのピーク幅が広がっている。これは、加圧することによって、混合物に含まれる結晶子（細かい一つ一つの粒）が歪むためである。圧力が４ＧＰａで、加熱温度が５５０℃のときに、エネルギーが７２ｅＶ付近に新たに回折ピークが出現した。このピークは、さらに加熱温度を上げると、加熱温度が７４０℃のときに消失した。この結果より、４ＧＰａの圧力下で、混合物を７４０℃に加熱すると、ＢｉＭｎＯ₃は融解することがわかった。
【００４９】
〔比較例１〕
１モルのＢ₂Ｏ₃と、１モルのＢｉ₂Ｏ₃と、１モルのＭｎ₂Ｏ₃とを、メノウの乳鉢を用いて混合し、混合物を得た。次に、混合物を、表２に示す圧力下で加熱したときのＸ線回折パターンについて、白色Ｘ線を用いたエネルギー分散法で調べた。その結果を図５に示す。
【００５０】
【表２】

【００５１】
図５に示すように、高圧域になるにしたがって、回折パターンのピーク幅が広がっている。これは、加圧することによって、混合物に含まれる結晶子（細かい一つ一つの粒）が歪むためである。圧力が４ＧＰａで、加熱温度が７００℃のときに、エネルギーが６７ｅＶ付近に新たに回折ピークが出現した。このピークは、さらに加熱温度を上げると、加熱温度が８２０℃のときに消失した。この結果より、４ＧＰａの圧力下で、混合物を８２０℃に加熱すると、ＢｉＭｎＯ₃は融解することがわかった。
【００５２】
【発明の効果】
本発明のＢｉＭｎＯ₃結晶の合成方法は、以上のように、Ｂ₂Ｏ₃とＨ₃ＢＯ₃とをフラックスとして用い、上記Ｂ₂Ｏ₃およびＨ₃ＢＯ₃と、Ｂｉ₂Ｏ₃と、Ｍｎ₂Ｏ₃との混合物を３ＧＰａ以上の圧力下で融解するフラックス混合融解工程と、上記融解によって生じた融解生成物を上記圧力下で徐冷する徐冷工程とを含む構成である。
【００５３】
それゆえ、Ｂ₂Ｏ₃とＨ₃ＢＯ₃とをフラックスとして用い、Ｂ₂Ｏ₃およびＨ₃ＢＯ₃と、Ｂｉ₂Ｏ₃と、Ｍｎ₂Ｏ₃との混合物を融解することで、ＢｉＭｎＯ₃を結晶として得ることができる。また、融解時に、フラックスとして用いたＢ₂Ｏ₃とＨ₃ＢＯ₃との反応によってＢ₂Ｏ₃と水分（Ｈ₂Ｏ）とが生じる。このＢ₂Ｏ₃と水分とによって、例えばカプセルの材料である金あるいは白金と、Ｂｉ₂Ｏ₃のビスマス（Ｂｉ）とが反応する温度よりも、Ｂｉ₂Ｏ₃とＭｎ₂Ｏ₃との融点を低くすることができる。したがって、カプセルを溶かすことなく、Ｂｉ₂Ｏ₃とＭｎ₂Ｏ₃とを融解させることができる。そして、融解によって生じた融解生成物（融液）を徐冷することで、ＢｉＭｎＯ₃を結晶として安定に得ることができる。また、フラックスとして用いるＢ₂Ｏ₃とＨ₃ＢＯ₃との量を調整することで、水分量を正確にコントロールしながらＢｉ₂Ｏ₃とＭｎ₂Ｏ₃との融点を下げることができるという効果を奏する。
【００５４】
本発明のＢｉＭｎＯ₃結晶の合成方法は、以上のように、上記Ｂｉ₂Ｏ₃とＭｎ₂Ｏ₃との融点を８００℃以下にする構成である。
【００５５】
それゆえ、Ｂ₂Ｏ₃とＨ₃ＢＯ₃とを用いて融点を８００℃以下にすることで、カプセルを溶かすことなく、Ｂｉ₂Ｏ₃とＭｎ₂Ｏ₃とを効率よく融解させることができるという効果を奏する。
【００５６】
本発明のＢｉＭｎＯ₃結晶の合成方法は、以上のように、上記Ｂｉ₂Ｏ₃と上記Ｍｎ₂Ｏ₃との合計量を１００モル％としたとき、上記Ｂ₂Ｏ₃を１０モル％〜１００００モル％の範囲内で用いるとともに、上記Ｈ₃ＢＯ₃を１０モル％〜１００００モル％の範囲内で用いる構成である。
【００５７】
それゆえ、Ｂ₂Ｏ₃とＨ₃ＢＯ₃とをそれぞれ上記範囲内で用いることで、ＢｉＭｎＯ₃の結晶を効率よく得ることができるという効果を奏する。
【００５８】
本発明のＢｉＭｎＯ₃結晶の合成方法は、以上のように、上記徐冷工程においては上記融解生成物の温度が６００℃以下になるまで徐冷する構成である。
【００５９】
それゆえ、融解生成物の温度が６００℃以下になるまで徐冷することで、ＢｉＭｎＯ₃の結晶をより効率よく得ることができるという効果を奏する。
【図面の簡単な説明】
【図１】実施例１で得られた結晶のＸ線回折振動を示す図である。
【図２】実施例１で得られた結晶の等温磁化曲線を示すグラフである。
【図３】実施例１で得られた結晶の０．５Ｔの磁場における磁化率温度変化を示すグラフである。
【図４】実施例９で得られた混合物のＸ線回折パターンである。
【図５】比較例１で得られた混合物のＸ線回折パターンである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to synthetic methods and BiMnO ₃ composition for crystal synthesis BiMnO ₃ crystals.
[0002]
[Prior art]
Ferromagnetic ferroelectrics that have both properties of ferromagnetism and ferroelectricity are expected to become devices that can control magnetism with an electric field, and conversely, control dielectric properties with a magnetic field. Further, since the ferromagnetic ferroelectric material has the second-order nonlinear optical effect exhibited by the ferroelectric material, it can be used as an optical switch whose characteristics can be controlled by a magnetic field. Unfortunately, however, materials that become ferromagnetic ferroelectrics are very rare because magnetism and dielectric properties are generally incompatible.
[0003]
By the way, for example, T. Atou et al, J. Solid State Chem. 145 (1999) 639 discloses that BiMnO ₃ is a ferromagnetic material having a transition point at 110K. Further, for example, R Seshadri and NA Hill, Chem . Mater. 13 (2001) in 2892, and the theoretical calculation of BiMnO _3, by a measurement of the preliminary dielectric constant using BiMnO ₃ powder, transition BiMnO ₃ is a 773K It is disclosed that it is a ferroelectric with temperature. Based on these, it is suggested that BiMnO ₃ is likely to be one of ferromagnetic ferroelectrics.
[0004]
Conventionally, a method of synthesizing BiMnO ₃ by a solid phase reaction between Bi ₂ O ₃ and Mn ₂ O ₃ under a high pressure of ₃ GPa is known. In this method, in order to protect from the reducing atmosphere created by the heater, Bi ₂ O ₃ and Mn ₂ O ₃ are sealed in a capsule made of gold (Au) or platinum (Pt) and then subjected to high-temperature and high-pressure treatment. BiMnO ₃ is synthesized by the above. According to this method, BiMnO ₃ is obtained in the form of a powder sintered body. A method of obtaining a BiMnO ₃ thin film using an excimer laser ablation method is disclosed in E. Ohshima et al, Solid State Communications 116 (2000) 73.
[0005]
[Problems to be solved by the invention]
However, the conventional method of synthesizing BiMnO ₃ has a problem that BiMnO ₃ cannot be obtained as a bulk (bulk) crystal that is not a thin film.
[0006]
For example, VA Bokov et al., Soviet Phys. Solid Chem. 1409 (1970) discloses a method for obtaining BiMnO ₃ as crystals from a melt of Bi ₂ O ₃ and Mn ₂ O ₃ under normal pressure. ing. However, as described in H. Chiba et al., Journal of Solid State Chemistry 132, 139-143 (1997), this method stably obtains BiMnO ₃ crystals due to poor reproducibility. I can't.
[0007]
BiMnO ₃ crystals are obtained by melting Bi ₂ O ₃ and Mn ₂ O ₃ at 950 ° C. or higher in the conventional method of synthesizing BiMnO ₃ under a high pressure of ₃ GPa, and resulting molten product (melt). It is thought that it can be obtained by slow cooling. However, in this case, before Bi ₂ O ₃ and Mn ₂ O ₃ are melted, in other words, at a temperature lower than the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ , gold or platinum as the material of the capsule is used. And Bi ₂ O ₃ bismuth (Bi) react to dissolve the capsule. Therefore, Bi ₂ O ₃ and Mn ₂ O ₃ cannot be melted, so that BiMnO ₃ crystals cannot be obtained.
[0008]
The present invention has been made in view of the above conventional problems, a method of synthesizing the purpose BiMnO ₃ crystal can be obtained stably BiMnO ₃ as crystals, as well as providing BiMnO ₃ composition for crystal synthesis There is.
[0009]
[Means for Solving the Problems]
The BiMnO ₃ crystal synthesis method of the present invention uses B ₂ O ₃ and H ₃ BO ₃ as fluxes in order to solve the above problems, and the B ₂ O ₃ and H ₃ BO ₃ and Bi ₂ O _{3 are used.} And a flux mixing and melting step in which a mixture of Mn ₂ O ₃ is melted under a pressure of ₃ GPa or more, and a slow cooling step in which the molten product generated by the melting is slowly cooled under the pressure. Yes.
[0010]
According to the above configuration, using B ₂ O ₃ and H ₃ BO ₃ as a flux, melting a mixture of B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ in the time of melting, B ₂ O ₃ and water by reaction of B ₂ O ₃ and H ₃ BO ₃ was used as a flux (H ₂ O) and results. The melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is higher than the temperature at which, for example, gold or platinum, which is a capsule material, reacts with bismuth (Bi) of Bi ₂ O _{3 due to} this B ₂ O ₃ and moisture. Can be lowered. Therefore, Bi ₂ O ₃ and Mn ₂ O ₃ can be melted without dissolving the capsule. The melt product produced by the melting (melt) by slow cooling, can be obtained stably BiMnO ₃ as crystals. Further, by adjusting the amounts of B ₂ O ₃ and H ₃ BO ₃ used as the flux, the melting points of Bi ₂ O ₃ and Mn ₂ O ₃ can be lowered while accurately controlling the water content.
[0011]
The BiMnO ₃ crystal synthesis method of the present invention is characterized in that the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is 800 ° C. or lower in order to solve the above-mentioned problems.
[0012]
According to the above configuration, Bi ₂ O ₃ and Mn ₂ O ₃ can be efficiently melted without melting the capsule by adding B ₂ O ₃ and H ₃ BO ₃ to a melting point of 800 ° C. or lower. Can be made.
[0013]
The method of synthesizing BiMnO ₃ crystals of the present invention, in order to solve the above problems, when the total amount of the Bi ₂ O ₃ and the Mn ₂ O ₃ as 100 mol%, the B ₂ O ₃ 10 mol The H ₃ BO ₃ is used in the range of 10 mol% to 10000 mol%.
[0014]
According to the above structure, B ₂ O ₃ and H ₃ BO ₃ and respectively with the use in the above-mentioned range, it is possible to efficiently obtain crystals BiMnO _3.
[0015]
The BiMnO ₃ crystal synthesis method of the present invention is characterized in that, in order to solve the above-mentioned problems, in the slow cooling step, the molten product is gradually cooled until the temperature of the molten product becomes 600 ° C. or lower.
[0016]
According to the above configuration, since the temperature of the melt product is gradually cooled until 600 ° C. or less, it can be obtained more efficiently crystals BiMnO _3.
[0017]
The composition for synthesizing BiMnO ₃ crystal of the present invention is characterized by comprising B ₂ O ₃ , H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ .
[0019]
In the composition for synthesizing BiMnO ₃ crystal of the present invention, when the total amount of Bi ₂ O ₃ and Mn ₂ O ₃ is 100 mol%, the B ₂ O ₃ is 10 mol% to 10000 mol%. Within the range, the H ₃ BO ₃ is preferably in the range of 10 mol% to 10000 mol%.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The BiMnO ₃ crystal synthesis method of the present invention (hereinafter simply referred to as “the present synthesis method”) uses B ₂ O ₃ and H ₃ BO ₃ as fluxes, B ₂ O ₃ and H ₃ BO ₃ , and Bi _2. and O _3, mixtures and flux mixture melting step of melting under a pressure of more than 3GPa of the Mn ₂ O _3, a melt product produced by the melt in a configuration that includes a slow cooling step of slow cooling under the pressure is there.
[0022]
Also in this synthesis method, the synthesis is performed under a pressure of ₃ GPa or more, as in the conventional synthesis method of BiMnO ₃ . This is because the BiMnO ₃ phase does not exist under a pressure of less than ₃ GPa. Further, when Bi ₂ O ₃ and Mn ₂ O ₃ are melted, Bi ₂ O ₃ and Mn ₂ O ₃ are made of gold to protect Bi ₂ O ₃ and Mn ₂ O ₃ from the reducing atmosphere created by the heater. The capsule is made of (Au) or platinum (Pt). In this synthesis method, B ₂ O ₃ and H ₃ BO ₃ are further used as flux. Therefore, B ₂ O ₃ and H ₃ BO ₃ are also enclosed in the capsule, and B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ are mixed to form a mixture, Melt. The melt product produced by the melting (melt) by slow cooling, can be obtained BiMnO ₃ as crystals.
[0023]
Thus, in this synthesis method, a mixture of B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ is melted using B ₂ O ₃ and H ₃ BO ₃ as flux. By doing so, B ₂ O ₃ and moisture (H ₂ O) are generated by the reaction between B ₂ O ₃ and H ₃ BO ₃ used as a flux during melting. The melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is higher than the temperature at which gold or platinum, which is the material of the capsule, reacts with bismuth (Bi) of Bi ₂ O _{3 due to} the B ₂ O ₃ and moisture. Becomes lower. Therefore, Bi ₂ O ₃ and Mn ₂ O ₃ can be melted without dissolving the capsule. The melt product produced by the melting (melt) by slow cooling, can be obtained stably BiMnO ₃ as crystals. Further, by adjusting the amounts of B ₂ O ₃ and H ₃ BO ₃ used as the flux, the melting points of Bi ₂ O ₃ and Mn ₂ O ₃ can be lowered while accurately controlling the water content.
[0024]
At this time, it is more preferable that the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is 800 ° C. or lower. By setting the melting point to 800 ° C. or less, Bi ₂ O ₃ and Mn ₂ O ₃ can be efficiently melted without dissolving the capsule.
[0025]
In this synthesis method, the pressure in the flux mixing and melting step and the slow cooling step may be 3 GPa or more, but more preferably 4.5 GPa or more. However, since it is technically difficult to generate a pressure exceeding 6 GPa, the upper limit of the pressure is more preferably 6 GPa.
[0026]
B ₂ O ₃ , H ₃ BO ₃ , Bi ₂ O ₃ , and Mn ₂ O ₃ used in this synthesis method are not particularly limited, and for example, a commercially available powdered product may be used.
[0027]
Further, the amounts of Bi ₂ O ₃ and Mn ₂ O ₃ are not particularly limited, and may be appropriately set as necessary. The ratio of Mn ₂ O ₃ for Bi ₂ O ₃ is not particularly limited, may be appropriately set as needed, to perform a flux mixture melting process efficiently, at least Bi ₂ O ₃ It is more preferable to use 1 mol or more of Mn ₂ O ₃ with respect to 1 mol.
[0028]
B ₂ O ₃ used as flux, the total amount of Bi ₂ O ₃ and Mn ₂ O ₃ (hereinafter, together with Bi ₂ O ₃ and Mn ₂ O ₃ as "the main raw material") with respect to 100 mole% More preferably, it is used within the range of 10 mol% to 10000 mol%, and more preferably within the range of 50 mol% to 500 mol%. By setting B ₂ O ₃ to be used within the above range, BiMnO ₃ crystals can be obtained efficiently. When the lower limit value of B ₂ O ₃ used for 100 mol% of the main raw material is less than 10 mol%, the melting points of Bi ₂ O ₃ and Mn ₂ O ₃ cannot be lowered sufficiently. Bi ₂ O ₃ Bi and the capsule may react to cause the capsule to melt. The main when raw material used for the 100 mole% upper limit of B ₂ O ₃ exceeds 10000 mole percent, would be the amount of B ₂ O ₃ is too large for the main raw material, as a result, obtained BiMnO ₃ The amount of crystals may be reduced.
[0029]
Further, H ₃ BO ₃ used as flux, the main raw material 100 mol%, more preferably used in the range of 10 mole% 10,000 mol%, be used within the scope of 50 mol% to 500 mol% Is more preferable. By setting H ₃ BO ₃ to be used within the above range, BiMnO ₃ crystals can be obtained efficiently. When the lower limit value of H ₃ BO ₃ used for 100 mol% of the main raw material is less than 10 mol%, the melting points of Bi ₂ O ₃ and Mn ₂ O ₃ cannot be lowered sufficiently. Bi ₂ O ₃ Bi and the capsule may react to cause the capsule to melt. On the other hand, when the upper limit value of H ₃ BO ₃ used with respect to 100 mol% of the main raw material exceeds 10,000 mol%, the amount of H ₃ BO ₃ with respect to the main raw material is too large. As a result, BiMnO ₃ obtained The amount of crystals may be reduced.
[0030]
In the flux mixing and melting step, the lower limit value of the heating temperature when melting the flux and the main raw material is not particularly limited as long as it is a temperature at which the mixture can be completely melted to obtain a molten product. When the heating temperature is too low, no melting product is produced, and as a result, BiMnO ₃ crystals cannot be obtained. The upper limit of the heating temperature is preferably 850 ° C. When the heating temperature exceeds the upper limit value, Bi ₂ O ₃ Bi reacts with the capsule before the melted product is formed, and the capsule may melt, which is not preferable.
[0031]
Moreover, in order to melt a mixture, it is more preferable to maintain the said heating temperature for 10 minutes or more. Thereby, the mixture can be completely melted.
[0032]
In the slow cooling step, the molten product (melt) is gradually cooled under the above pressure until BiMnO ₃ crystals are obtained. The slow cooling rate may be, for example, in the range of 10 ° C./hour to 33 ° C./hour. Thereby, the molten product can be efficiently cooled slowly. The slow cooling method is not particularly limited, but a method of slow cooling by gradually lowering the heating temperature by the heater is more preferable. BiMnO ₃ crystals can be efficiently obtained by sufficiently slowly cooling the molten product. At this time, it is more preferable to slowly cool the molten product until the temperature of the melted product is at least 600 ° C. or less, since BiMnO ₃ crystals can be obtained more efficiently.
[0033]
As described above, according to this synthesis method, BiMnO ₃ can be obtained as crystals. Moreover, since the obtained crystal is 0.1 mm square or more, it is possible to evaluate a device using this crystal.
[0034]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these.
[0035]
1. Synthesis of BiMnO ₃ crystal [Example 1]
0.9 moles of B ₂ O ₃ and 0.2 moles of H ₃ BO ₃ , 1 mole of Bi ₂ O ₃ , and 1 mole of Mn ₂ O ₃ were mixed using an agate mortar and the mixture Got. Next, the mixture was sealed in a platinum capsule, and the mixture was heated at 800 ° C. for 10 minutes under a pressure of 4 GPa using a cubic anvil type high pressure generator to obtain a molten product. After completion of the heating, the molten product was gradually cooled to 500 ° C. over 10 hours under the same pressure. Then, the mixture was further allowed to cool, the pressure was released after the molten product reached room temperature, and the molten product was taken out. Since the obtained melted product contains a flux, the melted product was washed with distilled water and ethanol and dried, and then crystals were taken out from the melted product. Using a microscope, a well-shaped cubic crystal was selected, and an X-ray diffraction experiment was performed on the obtained crystal. The result is shown in FIG.
[0036]
FIG. 1 shows the X-ray diffraction vibration of the obtained crystal. From the figure, the lattice constants of the obtained crystals were indexed by monoclinic crystals with a = 9.5800Å, b = 5.629Å, c = 9.895Å, β = 1100.548 °. This lattice constant was in good agreement with the lattice constant of BiMnO ₃ disclosed in T. Atou et al., Journal of Solid State Chemistry 145, 639 (1999).
[0037]
Next, the magnetic susceptibility of the crystal when the magnetic field applied to the crystal was changed at temperatures of 5K, 100K, and 150K was examined. The result is shown in FIG. Further, the magnetic susceptibility of the crystal with respect to temperature change when a magnetic field of 0.5 T was applied to the crystal was examined. The result is shown in FIG. The isothermal magnetization curve shown in FIG. 2 and the susceptibility temperature change shown in FIG. 3 showed good agreement with the known isothermal magnetization curve and susceptibility temperature change of the known BiMnO ₃ powder sintered body, respectively. From the above results, it was confirmed that the obtained crystal was BiMnO ₃ .
[0038]
[Example 2]
Crystals were obtained in the same manner as in Example 1 except that the mixture was heated to 800 ° C. and immediately subjected to a slow cooling step. Then, when the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined, it was confirmed that the obtained crystal was BiMnO ₃ .
[0039]
Example 3
Crystals were obtained in the same manner as in Example 2 except that the molten product was gradually cooled over 6 hours. Then, when the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined, it was confirmed that the obtained crystal was BiMnO ₃ .
[0040]
Example 4
0.88 mol of B ₂ O ₃ and 0.24 mol of H ₃ BO ₃ , 1 mol of Bi ₂ O ₃ and 1 mol of Mn ₂ O ₃ were mixed using an agate mortar, and the mixture Got. Next, the mixture was sealed in a platinum capsule, and the mixture was heated at 850 ° C. for 10 minutes under a pressure of 4 GPa using a cubic anvil type high pressure generator to obtain a molten product. After completion of the heating, the molten product was gradually cooled to 600 ° C. over 10 hours under the same pressure. Then, the mixture was further allowed to cool, the pressure was released after the molten product reached room temperature, and the molten product was taken out. In the same manner as in Example 1, after washing and drying the molten product, the crystal was taken out from the molten product, and the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined. Was confirmed to be BiMnO ₃ .
[0041]
Example 5
2.6 / 3 moles of B ₂ O ₃ and 0.8 / 3 moles of H ₃ BO ₃ , 1 mole of Bi ₂ O ₃ and 1 mole of Mn ₂ O ₃ using an agate mortar Mix to obtain a mixture. Next, the mixture was sealed in a platinum capsule, and the mixture was heated at 800 ° C. for 10 minutes under a pressure of 4 GPa using a cubic anvil type high-pressure generator to obtain a molten product. After completion of the heating, the molten product was gradually cooled to 600 ° C. over 12.5 hours under the same pressure. Then, the mixture was further allowed to cool, the pressure was released after the molten product reached room temperature, and the molten product was taken out. In the same manner as in Example 1, after washing and drying the molten product, the crystal was taken out from the molten product, and the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined. Was confirmed to be BiMnO ₃ .
[0042]
Example 6
Crystals were obtained in the same manner as in Example 5 except that the molten product was gradually cooled over 10 hours. And when the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined, it was confirmed that the obtained crystal was BiMnO ₃ .
[0043]
Example 7
2.5 / 3 moles of B ₂ O ₃ and 1/3 moles of H ₃ BO ₃ , 1 mole of Bi ₂ O ₃ , and 1 mole of Mn ₂ O ₃ were mixed using an agate mortar. A mixture was obtained. Next, the mixture was sealed in a platinum capsule, and the mixture was heated at 850 ° C. for 10 minutes under a pressure of 5 GPa using a cubic anvil type high pressure generator to obtain a molten product. After completion of the heating, the molten product was gradually cooled to 600 ° C. over 10 hours under the same pressure. Then, it was further allowed to cool, the pressure was released after the molten product reached room temperature, and the molten product was taken out. In the same manner as in Example 1, after washing and drying the molten product, the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined from the molten product. As a result, the obtained crystal was BiMnO ₃ . It was confirmed that there was.
[0044]
Example 8
0.8 moles of B ₂ O ₃ and 0.4 moles of H ₃ BO ₃ , 1 mole of Bi ₂ O ₃ and 1 mole of Mn ₂ O ₃ were mixed using an agate mortar, Got. Next, the mixture was sealed in a platinum capsule, and the mixture was heated at 790 ° C. for 10 minutes under a pressure of 4 GPa using a cubic anvil type high pressure generator to obtain a molten product. After completion of the heating, the molten product was gradually cooled to 600 ° C. over 19 hours under the same pressure. Then, it was further allowed to cool, the pressure was released after the molten product reached room temperature, and the molten product was taken out. In the same manner as in Example 1, after washing and drying the molten product, the crystal was taken out from the molten product, and the X-ray diffraction experiment of the crystal and the magnetic susceptibility of the crystal were examined. Was confirmed to be BiMnO ₃ .
[0045]
2. Examples and Comparative Examples are shown below BiMnO ₃ melting point of the crystal, by using the B ₂ O ₃ and H ₃ BO _3, it was confirmed that the melting point of BiMnO ₃ decreases.
[0046]
Example 9
2.6 / 3 moles of B ₂ O ₃ and 0.8 / 3 moles of H ₃ BO ₃ , 1 mole of Bi ₂ O ₃ and 1 mole of Mn ₂ O ₃ using an agate mortar Mix to obtain a mixture. Next, an X-ray diffraction pattern when the mixture was heated under the pressure shown in Table 1 was examined by an energy dispersion method using white X-rays. The result is shown in FIG.
[0047]
[Table 1]

[0048]
As shown in FIG. 4, the peak width of the diffraction pattern increases as the high pressure region is reached. This is because the crystallites (fine particles) contained in the mixture are distorted by pressurization. When the pressure was 4 GPa and the heating temperature was 550 ° C., a new diffraction peak appeared with an energy near 72 eV. This peak disappeared when the heating temperature was 740 ° C. when the heating temperature was further increased. From this result, it was found that when the mixture was heated to 740 ° C. under a pressure of 4 GPa, BiMnO ₃ was melted.
[0049]
[Comparative Example 1]
1 mol of B ₂ O ₃ , 1 mol of Bi ₂ O ₃ and 1 mol of Mn ₂ O ₃ were mixed using an agate mortar to obtain a mixture. Next, the X-ray diffraction pattern when the mixture was heated under the pressure shown in Table 2 was examined by an energy dispersion method using white X-rays. The result is shown in FIG.
[0050]
[Table 2]

[0051]
As shown in FIG. 5, the peak width of the diffraction pattern increases as the high pressure region is reached. This is because the crystallites (fine particles) contained in the mixture are distorted by pressurization. When the pressure was 4 GPa and the heating temperature was 700 ° C., a new diffraction peak appeared at an energy near 67 eV. This peak disappeared when the heating temperature was 820 ° C. when the heating temperature was further increased. From this result, it was found that when the mixture was heated to 820 ° C. under a pressure of 4 GPa, BiMnO ₃ was melted.
[0052]
【The invention's effect】
As described above, the method of synthesizing the BiMnO ₃ crystal of the present invention uses B ₂ O ₃ and H ₃ BO ₃ as fluxes, and uses the above B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ , and Mn. _The composition includes a flux mixing and melting step in which a mixture with ₂ O ₃ is melted under a pressure of ₃ GPa or more, and a slow cooling step in which the molten product generated by the melting is gradually cooled under the pressure.
[0053]
Therefore, by using B ₂ O ₃ and H ₃ BO ₃ as fluxes and melting a mixture of B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ , BiMnO ₃ Can be obtained as crystals. Further, at the time of melting, B ₂ O ₃ and water by reaction of B ₂ O ₃ and H ₃ BO ₃ was used as a flux (H ₂ O) and results. The melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is higher than the temperature at which, for example, gold or platinum, which is a capsule material, reacts with bismuth (Bi) of Bi ₂ O _{3 due to} this B ₂ O ₃ and moisture. Can be lowered. Therefore, Bi ₂ O ₃ and Mn ₂ O ₃ can be melted without dissolving the capsule. The melt product produced by the melting (melt) by slow cooling, can be obtained stably BiMnO ₃ as crystals. Further, by adjusting the amounts of B ₂ O ₃ and H ₃ BO ₃ used as fluxes, the effect that the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ can be lowered while accurately controlling the amount of water. Play.
[0054]
As described above, the BiMnO ₃ crystal synthesis method of the present invention has a configuration in which the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is 800 ° C. or lower.
[0055]
Therefore, Bi ₂ O ₃ and Mn ₂ O ₃ can be efficiently melted without melting the capsule by using B ₂ O ₃ and H ₃ BO ₃ to have a melting point of 800 ° C. or lower. There is an effect.
[0056]
In the BiMnO ₃ crystal synthesis method of the present invention, as described above, when the total amount of Bi ₂ O ₃ and Mn ₂ O ₃ is 100 mol%, the B ₂ O ₃ is 10 mol% to 10000. In addition to being used in the range of mol%, the H ₃ BO ₃ is used in the range of 10 mol% to 10000 mol%.
[0057]
Therefore, by using B ₂ O ₃ and H ₃ BO ₃ within the above ranges, there is an effect that BiMnO ₃ crystals can be obtained efficiently.
[0058]
As described above, the BiMnO ₃ crystal synthesis method of the present invention is configured to gradually cool until the temperature of the molten product is 600 ° C. or lower in the slow cooling step.
[0059]
Therefore, by slowly cooling the melted product until the temperature of the melted product becomes 600 ° C. or lower, there is an effect that BiMnO ₃ crystals can be obtained more efficiently.
[Brief description of the drawings]
1 is a diagram showing X-ray diffraction vibrations of a crystal obtained in Example 1. FIG.
2 is a graph showing an isothermal magnetization curve of the crystal obtained in Example 1. FIG.
3 is a graph showing changes in magnetic susceptibility temperature in a magnetic field of 0.5 T of the crystal obtained in Example 1. FIG.
4 is an X-ray diffraction pattern of the mixture obtained in Example 9. FIG.
5 is an X-ray diffraction pattern of the mixture obtained in Comparative Example 1. FIG.

Claims (6)

B ₂ O ₃ and H ₃ BO ₃ are used as fluxes,
A flux mixing and melting step of melting the mixture of B ₂ O ₃ and H ₃ BO ₃ , Bi ₂ O ₃ and Mn ₂ O ₃ under a pressure of ₃ GPa or more;
A method of synthesizing BiMnO ₃ crystal, comprising a slow cooling step of slowly cooling the melted product generated by the melting under the pressure. The method for synthesizing BiMnO ₃ crystals according to claim 1, wherein the melting point of Bi ₂ O ₃ and Mn ₂ O ₃ is 800 ° C or lower. When the total amount of the Bi ₂ O ₃ and the Mn ₂ O ₃ is 100 mol%, the B ₂ O ₃ is used within a range of 10 mol% to 10000 mol%, and the H ₃ BO ₃ is 10 The method for synthesizing BiMnO ₃ crystal according to claim 1 or 2, wherein the method is used within a range of from mol% to 10,000 mol%. The method for synthesizing BiMnO ₃ crystal according to any one of claims 1 to 3, wherein in the slow cooling step, the molten product is gradually cooled until the temperature of the molten product becomes 600 ° C or lower. B ₂ O ₃ , H ₃ BO ₃ , Bi ₂ O ₃ And Mn ₂ O ₃ BiMnO characterized by comprising ₃ Composition for crystal synthesis. Bi ₂ O ₃ And the above Mn ₂ O ₃ When the total amount is 100 mol%, the above B ₂ O ₃ Is in the range of 10 mol% to 10000 mol%, and the above H ₃ BO ₃ The composition according to claim 5, wherein is in the range of 10 mol% to 10000 mol%.

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