JP2017095334A - Molecular metallic oxide cluster, molecular metallic oxide cluster crystal, molecular metallic oxide cluster crystal aggregate, molecule memory, crystal memory and molecular polarization formation method to molecular metallic oxide cluster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molecular metallic oxide cluster that molecular polarization is held stably and is stable structurally.SOLUTION: A molecular metallic oxide cluster includes: cluster skeletons having inclusion parts which are provided at a continuous hole and one open end side and another open end side in the continuous hole and can include a metal ion and a water molecule; the metal ion included in one side of the inclusion part; and the water molecule included in another side of the inclusion part. The molecular metallic oxide cluster has molecular polarization by deflection of the metal ion.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a molecular metal oxide cluster, a molecular metal oxide cluster crystal, a molecular metal oxide cluster crystal aggregate, a molecular memory, a crystal memory, and a method for forming molecular polarization into a molecular metal oxide cluster.

  In recent years, there has been a demand for further improvement in recording density in information recording media using a ferromagnetic material or a ferroelectric material. However, it is suggested that the recording density of the current information recording medium will reach the limit in the near future.

  Ferromagnetic materials and ferroelectric materials are used in recording media such as magnetic tape and ferroelectric memory (FeRAM). These recording media require unit cells having at least several tens of crystal structures in order to hold one piece of recording information. For this reason, there is a physical recording density limit due to miniaturization, and recording cannot be held at a size smaller than this. Moreover, it is because it has become difficult from the economical and technical viewpoints to form the recording units in a precise, reproducible and highly regular arrangement.

  Ferroelectrics are substances in which electric dipoles are aligned without an external electric field, and the direction can be controlled to an arbitrary direction and size by applying an external electric field. Ferroelectrics are capable of reversing the polarization at high speed, and thus are expected to be used in a wider range of devices than ferromagnetic materials. However, miniaturization technology is delayed compared to ferromagnetic materials.

  One of the ferroelectrics is a monomolecular dielectric. A monomolecular dielectric is a material that has a dielectric expression mechanism in one molecule and thereby exhibits ferroelectric properties and behavior. Here, the ferroelectric property / behavior means the expression of dielectric hysteresis and spontaneous polarization. As the monomolecular dielectric, a polyoxometalate (hereinafter, abbreviated as POM) molecule including one terbium ion can be given.

POM is a molecular metal oxide cluster having a ring-like structure. One of them, Preyssler type POM, is represented by [M ^{n +} : P ₅ W ₃₀ O ₁₁₀ ] ^{(15-n) −} . Here, M ^{n +} is a metal ion included in the P ₅ W ₃₀ O ₁₁₀ molecule.

  Preyssler-type POM molecules have two stable ion sites inside. The ions taken into the molecule are stably held at any site in the Preyssler type POM molecule.

  In the low temperature region, since the thermal energy G of the included ions is smaller than the potential barrier U formed between the ion stable sites in the molecule, the ions move from one site to the other site. I can't. As a result, polarization is formed and exhibits ferroelectric properties and behavior.

On the other hand, when the temperature is equal to or higher than the ferroelectric onset temperature T _{C, the} thermal energy G of the included ions becomes larger than the potential barrier U, so that the ions move from one site to the other site. be able to. As a result, the polarization disappears and becomes a paraelectric material. Here, the ferroelectric onset temperature refers to a temperature at which dielectric hysteresis and spontaneous polarization disappear in the process of temperature rise.

  For many years, this researcher has created various isomers of POM and studied their physical properties. As a result, special physical properties associated with ion fluctuations in the POM molecule have been found.

For example, Non-Patent Document 1 relates to “Dielectric properties of Polyoxometalate with ion fluctuation”. The temperature dependence of the dielectric constant of TbP ₅ W ₃₀ O ₁₁₀ , which is an example of [M ^{n +} P ₅ W ₃₀ O ₁₁₀ ] ^{(15-n) —} , which is a Preyssler type POM (Polyoxometalate), was investigated. It is disclosed that it fluctuates between two sites.

  Non-Patent Document 2 relates to Evaluation of a structural ion fluctuation in Preyssler-type polyoxometalate salt. The content is the same as in Non-Patent Document 1.

Non-Patent Document 3 relates to The effect of irradiation on a Preyssler-type Polyoxometalate. With respect to [{Nd (H ₂ O) _x } ₄ TbP ₅ W ₃₀ O ₁₁₀ }], a color change by X-ray irradiation is disclosed.

  Non-Patent Document 4 relates to “observation of local ion migration in Preyssler-type Polyoxometalate”. The content is the same as in Non-Patent Document 1.

Non-Patent Document 5 relates to “development of polyoxometalate K ₁₂ [Tb (P ₅ W ₃₀ O ₁₁₀ )] having an ion transfer mechanism”. The content is the same as in Non-Patent Document 1.

Non-Patent Document 6 relates to “Structure and magnetic properties of Preyssler POM, K ₁₂ [GdP ₅ W ₃₀ O ₁₁₀ ] including lanthanoid ions”. This is the result of the structure and magnetic properties of the system using Gd in the Preyssler type POM.

Non-Patent Document 7 relates to “Structure and physical property evaluation of Preyssler type POM, K ₁₂ [TbP ₅ W ₃₀ O ₁₁₀ ] including lanthanoid ions”. This is the result of the structure and magnetic properties of the system using Tb in the Preyssler type POM.

Non-Patent Document 8 relates to “dielectric evaluation of Preyssler type polyoxometalate, K ₁₂ [Tb (P ₅ W ₃₀ O ₁₁₀ )]”. The content is the same as in Non-Patent Document 1.

  Non-Patent Document 10 relates to “observation of ion migration and physical property investigation in Preyssler type polyoxometalate molecule”. The content is the same as in Non-Patent Document 1.

  Non-Patent Document 11 relates to Tb (III) Ion Motion in Preyssler-type Polyoxometalate. The content is the same as in Non-Patent Document 1. From the X-ray structural analysis and IR measurement, ions migrate between the two sites, but it was confirmed that the ions were localized at one of the sites when quenched. The content is the same as in Non-Patent Document 1.

Non-Patent Document 12 relates to Crystal structure and magnetic properties of a doughnut-shaped POM including Gadolinium (III). This is a result of the crystal structure and magnetic properties of a system using Gd in POM. The crystal structure of [GdP ₅ W ₃₀ O ₁₁₀ ] ¹²⁻ was identified.

Non-Patent Document 13 relates to Structures and Physical Properties of Novel Preyssler-Lanthanide Complexes. M.M. By the method of Pope et al., K ₁₂ [TbP ₅ W ₃₀ O ₁₁₀ ] in which the inclusion ions were replaced with Tb ions was hydrothermally synthesized, and the product was identified from the X-ray single crystal structure and FT-IR measurement.

Non-Patent Document 14 relates to “structure and physical properties of Preyssler-type polyoxometalate containing lanthanoid ions”. M.M. According to the method of Pope et al., K ₁₂ [MP ₅ W ₃₀ O ₁₁₀ ] (M = Gd, Tb, Sm) in which inclusion ions are substituted with any one of Gd, Tb, and Sm is hydrothermally synthesized. It is disclosed that the product was identified from X-ray single crystal structure analysis.

Non-Patent Document 15 relates to “physical properties of a placer type polyoxometalate having an ion transfer mechanism”. With respect to TbP ₅ W ₃₀ O ₁₁₀ , the temperature dependence of the IR spectrum was examined, and an absorption peak shift was obtained. In addition, the temperature dependence of dielectric properties was investigated. From these results, it is disclosed that Tb ions are found to fluctuate between two sites at room temperature.

Other related researcher reports include the following: For example, Non-Patent Document 16 describes Polyoxometalates with Internal Cavities: Redox Activity, Basicity, and Cation Encapsulation in [X ^{n +} P ₅ W ₃₀ O ₁₁₀ ] ^(15-n) -Preyssler Complexes, with X = Na ⁺ , Ca ²⁺ , Y ³⁺ , La ³⁺ , Ce ³⁺ , and Th ⁴⁺ . It is described that the two stable sites in the POM are crystallographically equivalent.

Non-Patent Document 17 relates to “Slow Proton Exchange in Aqueous Solution. Consequences of Protonation and Hydration within the Central Cavity of Preyssler Anion Derivatives, [M (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] ⁿ⁻ ”. In the Preyssler type POM encapsulating sodium ions, it is described that sodium ions are present at one site in the POM molecule and water molecules are present at the other site.

Non-Patent Document 18 relates to “Rigid Nonlabile Polyoxometalate Cryptates [ZP ₅ W ₃₀ O ₁₁₀ ] ^(15-n) —that Exhibit Unprecedented Selectivity for Certain Lanthanide and Other Multivalent Cations”. A method for synthesizing Preyssler POM encapsulating lanthanoid ions is described.

  Non-Patent Document 19 relates to Mononuclear Lanthanide Single-Molecule Magnets Based on Polyoxometalates. It is described that a POM cluster shows a magnetic hysteresis like a ferromagnet with one molecule (single molecule magnet, SMM).

  Further, Patent Document 1 relates to “information recording / reproducing method using structural conversion of dye aggregate”. A method for recording information in units of whether or not to form an aggregate and a method for recording and reproducing information using a single molecule are disclosed.

  Patent Document 2 relates to a “microstructure device”. A configuration in which polyoxometalate is arranged at a microstructure site and is applied to a memory by its redox is disclosed.

  Patent Document 3 relates to “nanostructured devices” and the like. An arrangement using polyoxometalate as a ligand coating to coat nanostructures is disclosed.

  However, no result is obtained in which the POM molecule is single and exhibits dielectric hysteresis. Furthermore, knowledge of how information recording, holding, and reading are performed has not been obtained.

JP 2008-10100 A JP 2009-517640 A JP 2008-505773 A

Chisato Kato et.al., 5th Asian Conference on Coordination Chemistry, 12-16 July 2015, The University of Hong Kong, Hong Kong Chisato Kato et.al., Pacifichem 2015 Chisato Kato et.al., Muon Study Group 2013 Kato Chisato, Complex Summer School 2015 Chisato Kato et al., Yamaguchi Symposium 2013 Kato Chisato et al., Spring Meeting 2012 Kato Chisato et al., Spring Meeting 2013 Kato Chisato et al., Spring Meeting 2014 Kato Chisato et al. Spring Meeting 2015 Chisato Kato et al. Chugoku-Shikoku Branch Conference 2014 Tosato Kato et al., Tohoku Games 2013 Chisato Kato et al., Japan-Russia Symposium 2011 Chisato Kato et al., Japan-Russia Symposium 2013 Chisato Kato et al., Molecular Chemistry Discussion 2012 Kasato Chisato et al., Molecular Chemistry Discussion Meeting 2014 Jorge A. Fernandez et al., J. Am. Chem. Soc., 2007, 129, 12244-12253 Kee-Chan Kim, Michael T. Pope, Gennaro J. Gama, and Michael H. Dickman, J. Am. Chem. Soc., 121, 11164 (1999) Inge Creaser, Mark C. Heckel, R. Jeffrey Neitz, Michael T. Pope, Inorg. Chem., 32, 1573 (1993) Murad A. AlDamen et.al., J. Am. Chem. Soc., 2008, 130, 8874

  The present invention provides a molecular metal oxide cluster in which molecular polarization is stably maintained and structurally stable, a crystal thereof and an aggregate thereof, a method of forming molecular polarization in the molecular metal oxide cluster, It is an object of the present invention to provide a molecular memory and a crystal memory using the molecular metal oxide cluster.

In view of the above circumstances, the present inventor has made trial and error to (1) a monomolecular dielectric material in which POM surrounding Tb exhibits a large dielectric hysteresis, and (2) having Na and H ₂ O. POM is a non-dielectric material, but it can be made into a monomolecular dielectric material by removing H ₂ O, and (3) a monomolecular dielectric that removes H ₂ O and has only Na exhibits dielectric hysteresis. The present invention was completed by discovering that it is a material and (4) molecular polarization can be formed by removing an H ₂ O and applying an external electric field to a POM having only Na. The present invention has the following configuration.

  (1) A cluster skeleton having a communication hole and an inclusion portion provided on one open end side and the other open end side in the communication hole, each of which can include metal ions and water molecules; A molecular metal oxide comprising a metal ion included in one of the contact portions and a water molecule included in the other of the inclusion portions, and having molecular polarization due to the bias of the metal ions cluster.

  (2) The molecular metal oxide cluster according to (1), wherein the cluster skeleton has a substantially flat spheroid shape, and the communication hole is provided along a rotation axis.

(3) The molecular metal oxide cluster according to (2), wherein the cluster skeleton is a polyoxometalate represented by the chemical formula P ₅ W ₃₀ O ₁₁₀ .

(4) The cluster skeleton is represented by the following chemical formula (1), and in the chemical formula (1), M1 is any metal ion selected from the group of alkali metals and lanthanoids (1) to (1) The molecular metal oxide cluster according to any one of 3).
M1, H ₂ O-P ₅ W ₃₀ O ₁₁₀ (1)

(5) The molecular metal oxide cluster according to (4), wherein M1 is any metal ion selected from the group consisting of Na ⁺ , Nd ³⁺ , Dy ^{3+ and} Tb ³⁺ .

  (6) A molecular metal oxide cluster crystal comprising the molecular metal oxide cluster according to any one of (1) to (5), a counter cation, and a water molecule.

  (7) The molecular metal oxide according to (6), wherein the water molecule includes coordinated crystal water coordinated to a counter cation and non-coordinated crystal water not coordinated to a counter cation. Cluster crystal.

  (8) The molecular metal oxide cluster crystal according to (6) or (7), wherein the molecular metal oxide cluster forms an orthorhombic crystal structure.

  (9) The molecular metal oxidation according to (8), comprising a counter cation coordinated with coordinated crystal water and non-coordinated crystal water between lattices of the orthorhombic crystal structure Cluster complex crystals.

(10) It is represented by the following chemical formula (2), and in the chemical formula (2), M1 is any metal ion selected from the group of Na ⁺ , Nd ³⁺ , Dy ³⁺ or Tb ³⁺ , and M2 is Na One, two or more cations selected from the group of ⁺ , K ⁺ , Ca ²⁺ , Ce ⁴⁺ or NH ₄ ⁺ , n is a natural number of 1 to 10 and m is 1 to 40 The molecular metal oxide cluster crystal according to any one of (6) to (9), which is a number.
_{M2, (H 2 O) n} [M1, H 2 O-P 5 W 30 O 110] · mH 2 O ··· (2)

  (11) A molecular metal oxide cluster crystal aggregate, wherein the molecular metal oxide cluster crystal according to any one of (6) to (10) is aggregated.

  (12) The molecular metal oxide cluster crystal aggregate according to (11), which is a pellet.

  (13) A molecular memory comprising the molecular metal oxide cluster according to any one of (1) to (5), wherein the magnitude and direction of molecular polarization in an external electric field 0 are used as recording units.

  (14) The molecular metal oxide cluster crystal according to any one of (6) to (10) is provided, and the total magnitude and direction of polarization per mass in an external electric field 0 are used as recording units. And crystal memory.

  (15) The molecular metal oxide cluster according to any one of (1) to (5) is heated in a vacuum, and the inclusion water molecule is taken out from the molecular metal oxide cluster to include the water molecule. A molecular metal oxide comprising: a step of forming a molecular metal oxide cluster that does not enclose, and a step of forming a polarization by applying an electric field to the molecular metal oxide cluster that does not include water molecules A method of forming molecular polarization into clusters.

  (16) The method for forming molecular polarization into a molecular metal oxide cluster according to (15), wherein the vacuum heating is performed at 80 ° C. or more and 140 ° C. or less.

  (17) The method for forming molecular polarization into a molecular metal oxide cluster according to (16), wherein the vacuum heating is performed at 120 ° C. or higher.

(18) The method of forming a molecular polarization into a molecular metal oxide cluster according to any one of (15) to (17), wherein the temperature is raised to the vicinity of the ferroelectric expression temperature T _C when an electric field is applied .

According to the molecular metal oxide cluster of the present invention, water molecules are included in the other inclusion portion of the communication hole, and movement of metal ions that cause a bias of charge in one inclusion portion is prevented. Therefore, the molecular polarization can be stably maintained. By removing H ₂ O from this molecular metal oxide cluster, dielectric hysteresis can be developed by applying an external electric field. After polarization, exposure to water vapor gas introduces water molecules into the POM, so that the polarization state can be stably maintained. Alternatively, the polarization state can be stably maintained by lowering the temperature. These can be used as a molecular memory.

  According to the molecular metal oxide cluster crystal of the present invention, since it has a counter cation and a water molecule, a crystal composed of a structurally stable molecular metal oxide cluster can be provided. Thus, it can be used as a crystal memory.

  According to the molecular metal oxide cluster crystal aggregate of the present invention, since a crystal composed of a structurally stable molecular metal oxide cluster is formed, a structurally stable aggregate can be provided.

According to the molecular memory of the present invention, a monomolecular dielectric can be obtained by removing H ₂ O from the molecular metal oxide cluster. By applying an external electric field, a molecular memory capable of stably maintaining molecular polarization in the external electric field 0 can be provided.

According to the crystal memory of the present invention, a monomolecular dielectric can be obtained by removing H ₂ O from the crystalline molecular metal oxide cluster. By applying an external electric field, the molecular polarization in the external electric field 0 for each molecule can be stably maintained, so that a crystal memory can be provided.

According to the method of forming a molecular polarization into a molecular metal oxide cluster of the present invention, by removing H ₂ O from a molecular metal oxide cluster having a metal ion and H ₂ O, which is a non-dielectric material, It can be a molecular dielectric. By applying an external electric field, molecular polarization can be formed in the molecular metal oxide cluster.

It is a figure which shows an example of the molecular metal oxide cluster crystal aggregate of embodiment of this invention, Comprising: It is sectional drawing (b) in the top view (a) and A-A 'line. It is the B section enlarged view (a) of FIG.1 (b), and the enlarged view (b) of the molecular metal oxide cluster crystal 11 of Fig.2 (a). It is the C section enlarged view of Drawing 2 (b), and is a crystal structure of a molecular metal oxide cluster crystal. It is a figure of the b-axis projection surface of the molecular metal oxide cluster crystal of FIG. It is a figure which shows an example of the molecular metal oxide cluster of embodiment of this invention, Comprising: It is a top view (a) and a side view (b). It is a figure explaining an example of the molecular polarization formed in the molecular metal oxide cluster of embodiment of this invention. It is process drawing explaining an example of the molecular polarization formation method to the molecular metal oxide cluster of embodiment of this invention. A diagram for explaining an example of the energy structure of the molecular metal oxide clusters embodiment of the present invention, <and T _C (a), the high temperature T> cold T is energy structure explanatory view of T _C (b) . It is process drawing explaining another example of the molecular polarization formation method to the molecular metal oxide cluster of embodiment of this invention. It is a figure explaining an example of the polarization of the crystal | crystallization formed in the molecular metal oxide cluster crystal of embodiment of this invention. It is a figure explaining an example of the polarization of the aggregate formed in the molecular metal oxide cluster crystal aggregate of embodiment of this invention. It is a photograph of the obtained crystal. It is a crystal structure diagram. It is a crystal structure diagram. It is a crystal structure diagram. It is IR spectrum measurement result of a Ce-NaPOM (no vacuum heat processing) sample and a Ce-NaPOM (vacuum 80 degreeC 2h process) sample. It is a graph which shows the temperature dependence of IR spectrum of a Ce-NaPOM (no vacuum heat processing) sample. It is an apparatus block diagram of a dielectric constant measurement. It is a graph which shows the temperature dependence of the dielectric loss obtained from the dielectric constant measurement of the Ce-NaPOM (no vacuum heat processing) sample. It is a graph which shows the temperature dependence of the dielectric loss obtained from the dielectric constant measurement of the Ce-NaPOM (vacuum 80 degreeC2h process) sample. It is an apparatus block diagram of a dielectric constant measurement. It is a graph which shows PT (temperature dependence of polarization) of a Ce-NaPOM (no vacuum heat treatment) sample and a Ce-NaPOM (vacuum 80 ° C., 2 h treatment) sample. It is a graph which shows PE (electric field dependence of polarization) of a Ce-NaPOM (no vacuum heat treatment) sample. It is a graph which shows PE of a Ce-NaPOM (vacuum 80 degreeC 2h process) sample. It is a graph which shows PE of a Ce-NaPOM (vacuum 120 degreeC 4h process) sample. It is a photograph of the obtained crystal. Graph (a) showing temperature dependence of dielectric loss obtained from dielectric constant measurement of K, Na-TbPOM sample, Arrhenius plot (b) obtained from temperature dependence of dielectric loss of K, Na-TbPOM sample It is. It is a graph (PT graph, temperature dependence graph of polarization) which shows the temperature dependence of the value which normalized the integrated value of the pyroelectric current of a K and Na-TbPOM sample with the integrated value of the pyroelectric current in 100K. It is a dielectric hysteresis loop of a K, Na-TbPOM sample. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal. It is a photograph of the obtained crystal.

(Embodiment)
Hereinafter, referring to the accompanying drawings, molecular metal oxide clusters, molecular metal oxide cluster crystals, molecular metal oxide cluster crystal aggregates, molecular memory, crystal memory and molecular metal according to embodiments of the present invention A method for forming molecular polarization into an oxide cluster will be described.

<Molecular metal oxide cluster crystal aggregate>
FIG. 1: is a figure which shows an example of the molecular metal oxide cluster crystal aggregate of embodiment of this invention, Comprising: It is a top view (a) and sectional drawing (b) in the AA 'line. As shown in FIG. 1, the molecular metal oxide cluster crystal aggregate 10 of the embodiment of the present invention is formed into a substantially disc-shaped pellet. However, the present invention is not limited to this, and a plate shape, a cubic pellet, or the like may be used.

  FIG. 2 is an enlarged view (b) of the B part in FIG. 1 (b) and an enlarged view (b) of the molecular metal oxide cluster crystal 11 in FIG. 2 (a). As shown in FIG. 2A, the molecular metal oxide cluster crystal aggregate of the embodiment of the present invention is formed by aggregating molecular metal oxide cluster crystals. For example, the molecular metal oxide cluster crystal 11 is pressed and formed into a pellet.

<Molecular metal oxide cluster crystals>
FIG. 3 is an enlarged view of a part C in FIG. 2B and shows a crystal structure of a molecular metal oxide cluster crystal. The molecular metal oxide cluster crystal 11 is a single crystal having a molecular metal oxide cluster 31, a counter cation, and a water molecule. The water molecules include coordinated crystal water coordinated to a counter cation and non-coordinated crystal water not coordinated to a counter cation.

  The molecular metal oxide cluster crystal 11 forms an orthorhombic crystal structure (Pnma). Between the lattices of the orthorhombic crystal structure, a counter cation coordinated with coordinated crystal water and non-coordinated crystal water are included. Part C is a c-axis projection plane of the molecular metal oxide cluster crystal.

  4 is a diagram of a b-axis projection plane of the molecular metal oxide cluster crystal of FIG. The communication holes 31c of the molecular metal oxide cluster 31 are laminated in the b-axis direction.

The counter cation is preferably selected from the group of Na ⁺ , K ⁺ , Ca ²⁺ , Ce ⁴⁺ or NH ₄ ⁺ and is one or more cations. The coordinating crystal water can be stably held by these counter cations, and even when the molecular metal oxide cluster crystal 11 is generated and taken out from the water, the large crystal can be stably maintained as it is without being cracked and shattered. Can hold.

The molecular metal oxide cluster crystal is represented by the chemical formula (2) described above, and in the chemical formula (2), M1 is any one selected from the group of Na ⁺ , Nd ³⁺ , Dy ³⁺ or Tb ³⁺ . M2 is one or more cations selected from the group consisting of Na ⁺ , K ⁺ , Ca ²⁺ , Ce ⁴⁺ or NH ₄ ⁺ , and n is a natural number of 1 or more and 10 or less M is a natural number of 1 or more and 40 or less.

<Molecular metal oxide clusters>
FIG. 5 is a view showing an example of the molecular metal oxide cluster according to the embodiment of the present invention, and is a plan view (a) and a side view (b). The molecular metal oxide cluster 31 has a cluster skeleton, a metal ion M1, and a water molecule.

  The cluster skeleton has a communication hole 31c, and inclusion portions 31c1 and 31c2 capable of inclusion of metal ions and water molecules are provided on one open end side and the other open end side in the communication hole 31c, respectively. Phosphorus-tungsten oxide molecule.

  In the molecular metal oxide cluster 31, the metal ion M1 is included in one of the inclusion portions 31c1 in the communication hole 31c, and the water molecule is included in the other 31c2.

  The cluster skeleton has a substantially flat spheroid shape, and communication holes 31c are provided along the rotation axis. Thereby, it is possible to increase the selectivity of the molecular polarization direction in the crystal forming the orthorhombic crystal structure (Pnma). That is, the selection of a random direction can be reduced, and the selectivity of unidirectional and vice versa can be increased.

As the cluster skeleton, a polyoxometalate molecule having a polyoxometalate skeleton and represented by the chemical formula P ₅ W ₃₀ O ₁₁₀ can be given. Preyssler type POM.

  The cluster skeleton is represented by the chemical formula (1) described above, and in the chemical formula (1), M1 is preferably any metal ion selected from the group of alkali metals and lanthanoids. Thereby, by taking out water molecules, a molecular metal oxide cluster serving as a monomolecular dielectric can be formed, and molecular polarization can be formed.

More preferably, M1 is any metal ion selected from the group of Na ⁺ , Nd ³⁺ , Dy ³⁺ or Tb ³⁺ . A molecular metal that becomes a monomolecular dielectric by taking out water molecules when the metal ion M1 is any metal ion selected from the group of Na ⁺ , Nd ³⁺ , Dy ^3+, or Tb ³⁺ An oxide cluster can be formed, molecular polarization can be formed, and the stability of the molecular metal oxide cluster can be enhanced.

The Na ⁺ molecular metal oxide cluster exhibited dielectric hysteresis by extracting water molecules. Molecular metal oxide clusters not containing water molecules of Tb ³⁺ showed large dielectric hysteresis. Nd ³⁺ and Dy ³⁺ are not easily disintegrated even when taken out from water, maintain a stable structure, and share the same dielectric hysteresis with Tb ³⁺ in terms of ionic radius, electronic properties, etc. This is because it can be estimated.

<Molecular memory>
FIG. 6 is a diagram illustrating an example of molecular polarization formed in the molecular metal oxide cluster according to the embodiment of the present invention. A molecular metal oxide cluster has a stable site of two metal ions. Since an energy barrier U exists between the two stable sites, a single molecule can take two polarization directions. When a metal ion is included in any one of the sites, molecular polarization is formed by the bias of the metal ion M1 in the molecular metal oxide cluster.

  Since water molecules are included in the other 31c2 of the inclusion part, the molecular polarization is stably maintained. In this state, since the metal ion M1 cannot move to the other site, the magnitude and direction of the polarization of the crystal cannot be controlled by the external electric field. However, a desired molecular polarization can be formed by the following molecular polarization formation method for molecular metal oxide clusters, and a molecular memory can be formed by controlling the total size and direction of the molecular polarization with an external electric field.

  The molecular memory according to the embodiment of the present invention is a molecular memory composed of molecular metal oxide clusters, and uses the magnitude and direction of molecular polarization in an external electric field 0 as a recording unit.

<Method of forming molecular polarization into molecular metal oxide cluster>
FIG. 7 is a process diagram illustrating an example of a method for forming molecular polarization into a molecular metal oxide cluster according to an embodiment of the present invention. The method of forming a molecular polarization into a molecular metal oxide cluster according to an embodiment of the present invention includes a step S1 of forming a molecular metal oxide cluster that does not include water molecules and a step S2 of applying an external electric field. And is roughly configured.

<Step S1 of forming a molecular metal oxide cluster that does not include water molecules>
In this step, the molecular metal oxide cluster is heated in vacuum, and the inclusion water molecules are taken out from the molecular metal oxide cluster to form a molecular metal oxide cluster that does not include water molecules. By taking out water molecules, it is possible to move metal ions from one clathrate to the other clathrate. That is, it is a metal ion migration enabling process.

  It is preferable to heat to 80 ° C. or higher and 140 ° C. or lower by vacuum heating. By heating to 80 ° C. or higher, at least a part of the inclusion water molecules can be taken out from the molecular metal oxide cluster to form a molecular metal oxide cluster that does not include water molecules. When heated to over 140 ° C., the molecular metal oxide clusters may collapse.

  It is more preferable to heat to 120 ° C. or higher by vacuum heating. Thereby, the inclusion water molecule can be taken out from a larger number of molecular metal oxide clusters than in the case of 80 ° C., and a molecular metal oxide cluster that does not include water molecules can be formed.

<Step S2 of applying an electric field>
This step is a molecular polarization forming step in which an external electric field is applied to a molecular metal oxide cluster that does not include water molecules to form molecular polarization.

FIG. 8 is a diagram for explaining an example of the energy structure of the molecular metal oxide cluster according to the embodiment of the present invention, in which the energy structure of low temperature T <T _C (a) and high temperature T> T _C (b). It is explanatory drawing. In molecular metal oxide clusters that do not include water molecules, the two ion-stable sites inside are crystallographically equivalent. As shown in FIG. 8 (a), since there is an energy barrier U between one site and the other site, the metal ion M1 can be easily formed even when an external electric field E is applied at a low temperature (T <T _C ). Does not move between sites. By trapping the metal ions at the respective sites, the polarization P in the opposite direction to the polarization P in one direction is formed and stably maintained in each state.

Thereby, even if it is low temperature, if a big external electric field is applied, desired molecular polarization can be formed.
However, as shown in FIG. 8B, when the temperature is raised to a temperature (T> T _C ) that easily exceeds the energy barrier U existing between the sites, the inter-site fluctuation of the metal ions becomes active. In this state, the desired molecular polarization can be easily formed even if the applied external electric field is small.

  The external electric field is preferably small in order to prevent reduction of POM molecules. This is because if a high voltage is applied too much (1600 V / cm or more), a redox reaction occurs in the POM skeleton. For example, the external electric field for forming a desired molecular polarization at room temperature is 600 V / cm.

<Step S3 for inclusion of water molecules>
FIG. 9 is a process diagram illustrating an example of a method for fixing molecular polarization to a molecular metal oxide cluster. As shown in FIG. 9A, after the formation of molecular polarization, a molecular metal oxide cluster that does not include water molecules may be exposed to water vapor gas to include water molecules. Inclusion of water molecules makes it impossible to move metal ions, and molecular polarization can be stably maintained.

  As shown in FIG. 9 (b), the step of lowering the molecular metal oxide cluster that does not include water molecules after the formation of molecular polarization may be included. By lowering the temperature, it becomes impossible to exceed the energy barrier U with the thermal energy of the metal ions, and the molecular polarization can be stably maintained.

<How to read molecular polarization from molecular metal oxide clusters>
The molecular polarization read-out method from the molecular metal oxide cluster can be achieved by bringing the one that senses either or both of the electric field and magnetic field generated by the molecular metal oxide cluster close to each other. Read the size and direction. Examples of sensors that sense either or both of electric and magnetic fields include ferroelectrics, ferromagnets, multiferroics, electromagnetic coils, etc., and mechanical or electromagnetics generated by bringing these close to metal oxide clusters. Can be read out by a typical action.

<Crystal memory>
FIG. 10 is a diagram illustrating an example of crystal polarization formed in the molecular metal oxide cluster crystal according to the embodiment of the present invention. A crystal 11 forming an orthorhombic crystal structure (Pnma) formed by a molecular metal oxide cluster formed by molecular polarization (Molecular Dipole moment) formed by the bias of the metal ion M1 is formed by each molecular metal oxide cluster. , With molecular polarization in either direction, or in the opposite direction. Depending on the total magnitude and direction of polarization per constant mass, crystal polarization is formed. A crystal memory can be formed by controlling the total magnitude and direction of crystal polarization by an external electric field.

  The crystal memory according to the embodiment of the present invention is a crystal memory composed of molecular metal oxide cluster crystals, and uses the total size and direction of polarization per mass in an external electric field 0 as a recording unit.

  FIG. 11 is a diagram illustrating an example of the polarization of the aggregate formed in the molecular metal oxide cluster crystal aggregate according to the embodiment of the present invention. Depending on the total magnitude and direction of polarization per constant mass, aggregate polarization is formed.

The molecular metal oxide cluster according to the embodiment of the present invention has a communication hole 31c, and can include metal ions M1 and water molecules on one open end side and the other open end side in the communication hole 31c, respectively. A molecular metal oxide cluster 31 composed of a molecular metal oxide cluster provided with various inclusion portions 31c1 and 31c2, a metal ion M1, and a water molecule, and one of the inclusion portions in the communication hole 31c Since the metal ion M1 is included in 31c1 and the water molecule is included in the other 31c2, and the molecular ion is caused by the bias of the metal ion M1 in the molecular metal oxide cluster 31, the other inclusion of the communication hole is included. Since the water molecules are included in the contact portion and the movement of the metal ion causing the bias of the charge in one of the inclusion portions to the other is prevented, the molecular polarization can be stably maintained. By removing H ₂ O from the molecular metal oxide cluster, a monomolecular dielectric can be obtained. After polarization, exposure to water vapor gas introduces water molecules into the POM, so that the polarization state can be stably maintained. Alternatively, the polarization state can be stably maintained by lowering the temperature. These can be used as a molecular memory.

  Since the molecular metal oxide cluster 31 according to an embodiment of the present invention has a configuration in which the molecular metal oxide cluster has a substantially flat spheroid shape and the communication hole 31c is provided along the rotation axis, When the is formed, the uniformity of polarization can be improved.

The molecular metal oxide cluster 31 according to the embodiment of the present invention has a configuration in which the molecular metal oxide cluster is a polyoxometalate represented by the chemical formula P ₅ W ₃₀ O ₁₁₀ , and thus when a single crystal is formed. Furthermore, the uniformity of polarization can be improved.

  In the molecular metal oxide cluster according to the embodiment of the present invention, the molecular metal oxide cluster 31 is represented by the chemical formula (1), and M1 is selected from the group of alkali metals and lanthanoids in the chemical formula (1). Therefore, by taking out water molecules, molecular metal oxide clusters that become monomolecular dielectrics can be formed, and molecular polarization can be formed.

Since the molecular metal oxide cluster 31 according to the embodiment of the present invention has a configuration in which M1 is any metal ion selected from the group of Na ⁺ , Nd ³⁺ , Dy ^3+, or Tb ³⁺ , The molecular metal oxide cluster that becomes a monomolecular dielectric can be formed by taking out, so that molecular polarization can be formed, and the stability of the molecular metal oxide cluster can be enhanced.

  The molecular metal oxide cluster crystal 11 according to an embodiment of the present invention has a molecular metal oxide cluster 31, a counter cation, and a water molecule, and thus includes a structurally stable molecular metal oxide cluster. Crystals can be provided. Thus, it can be used as a crystal memory.

  The molecular metal oxide cluster crystal 11 according to the embodiment of the present invention has a configuration including coordinated crystal water coordinated to a counter cation and non-coordinated crystal water not coordinated to a counter cation as the water molecule. Stable crystals can be formed.

  Since the molecular metal oxide cluster crystal 11 according to the embodiment of the present invention has a configuration in which the molecular metal oxide cluster 31 forms an orthorhombic crystal structure, the molecular polarization directions of the molecules can be aligned. .

  A molecular metal oxide cluster crystal 11 according to an embodiment of the present invention includes a counter cation coordinated with coordinated crystal water and non-coordinated crystal water between lattices of the orthorhombic crystal structure. Therefore, a stable structure can be formed without easily desorbing water molecules.

In the molecular metal oxide cluster crystal 11 according to the embodiment of the present invention, the molecular metal oxide cluster crystal 11 is represented by the chemical formula (2). In the chemical formula (2), M1 is Na ⁺ , Nd ³⁺ , Dy ^3. Any one or more metal ions selected from the group of ⁺ or Tb ³⁺ , wherein M2 is selected from the group of Na ⁺ , K ⁺ , Ca ²⁺ , Ce ⁴⁺ or NH ₄ ⁺ Since it is a cation, n is a natural number of 1 or more and 10 or less, and m is a natural number of 1 or more and 40 or less, a stable structure can be formed and a large polarization can be formed.

  Since the molecular metal oxide cluster crystal aggregate 10 according to the embodiment of the present invention has a configuration in which the molecular metal oxide cluster crystals 11 described above are aggregated, a structurally stable molecular metal oxide cluster is provided. Therefore, a structurally stable aggregate can be provided.

  Since the molecular metal oxide cluster crystal aggregate 10 according to the embodiment of the present invention is a pellet, it is easy to handle and can provide a structurally stable aggregate.

The molecular memory according to the embodiment of the present invention is a molecular memory composed of molecular metal oxide clusters 31 and has a structure in which the magnitude and direction of polarization in the external electric field 0 are used as recording units. By removing H ₂ O, a monomolecular dielectric can be formed, and by applying an external electric field, a molecular memory that can stably maintain the molecular polarization in the external electric field 0 can be provided.

The crystal memory according to the embodiment of the present invention is a crystal memory composed of molecular metal oxide cluster crystals 11 and has a configuration in which the total magnitude and direction of polarization per unit mass in the external electric field 0 is a recording unit. By removing H ₂ O from the molecular metal oxide cluster of the crystal, it can be made a monomolecular dielectric, and by applying an external electric field, the molecular polarization in the external electric field 0 for each molecule can be stably maintained. Crystal memory can be provided.

In the molecular polarization forming method for the molecular metal oxide cluster 31 according to the embodiment of the present invention, the molecular metal oxide cluster 31 is heated in a vacuum, and the inclusion water molecules are exposed from the molecular metal oxide cluster 31 to the outside. Step S1 of forming a molecular metal oxide cluster that does not include water molecules and applying electric field to the molecular metal oxide cluster that does not include water molecules to form polarization S2. Since it has a configuration, it can be made a monomolecular dielectric by removing H ₂ O from POM having a metal ion, H ₂ O, which is a non-dielectric material, and a molecular metal by applying an external electric field Molecular polarization can be formed in the oxide cluster.

Since the molecular polarization forming method for the molecular metal oxide cluster 31 according to the embodiment of the present invention is configured to heat to 80 ° C. or higher and 140 or lower by vacuum heating, the metal without breaking down the molecular metal oxide cluster. At least a portion of H ₂ O can be removed from the POM with ions, H ₂ O.

Molecular polarizability forming method of the molecular metal oxide clusters 31 which is an embodiment of the present invention, by vacuum heating, the structure is heated to above 120 ° C., remove most of the H ₂ O from POM having of H ₂ O be able to.

In the molecular polarization forming method for the molecular metal oxide cluster according to the embodiment of the present invention, when an electric field is applied, the temperature is raised to near the ferroelectric expression temperature T _C , so that polarization can be easily formed even with a small external electric field. it can. Molecular polarization can be formed efficiently. The temperature rise may theoretically be the same temperature as the ferroelectric onset temperature Tc, but it may be raised to a temperature exceeding the ferroelectric onset temperature Tc by about 10 ° C., or a temperature lower by about 10 ° C. is sufficient. An effect is obtained.

  Molecular metal oxide cluster, molecular metal oxide cluster crystal, molecular metal oxide cluster crystal aggregate, molecular memory, crystal memory and molecular polarization forming method for molecular metal oxide cluster according to embodiments of the present invention The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical idea of the present invention. Specific examples of this embodiment are shown in the following examples. However, the present invention is not limited to these examples.

Example 1
<Single crystal production>
First, [K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] .15H ₂ O], which is a Preyssler type POM encapsulating sodium ions, was synthesized by a method already reported. Next, 3 ml of H ₂ O was added to 61.0 mg (0.140 mmol) of Ce (NO ₃ ) ₃ .6H ₂ O to prepare a first solution. Next, 12 ml of H ₂ O was added to 1.00 g (0.121 mmol) of K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] · 15H ₂ O to prepare solution B, and the second solution was added to 60 ml. Heated to ° C. Next, the 2nd solution was dripped at the 1st solution, and the 1st mixed solution was prepared. Next, the first mixed solution was held at 160 ° C. for 24 hours. Thus, a crystal powder was obtained.

  FIG. 12 is a photograph of the obtained crystal. A pale yellow transparent crystal having a longest diameter of 2 mm was obtained.

<X-ray structural analysis>
Structural analysis was performed using an X-ray structural analysis device (device name: SMART APEX II ULTRA diffractometer manufactured by Bruker). This device has a TXS rotating anode, and the TXS rotating anode has Mo Kα radiation, λ = 0.71073 mm, and has multilayer optics. Data collection was performed at 173 K under liquid nitrogen flow using a Japan Thermal Engineering DX-CS190LD N ₂ -gas-flow cryostat.

  The structure was analyzed by direct methods (SHELXL-97) and refined by full-matrix least-squares on F2 using SHELXL-97 (reference: J. Am. Chem. Soc. 2015, 137, 4477-4486).

  All H atoms were improved with riding models. Because of the undisturbed crystal structure, all non-H atoms were improved for anisotropy. Details of the improvement were given to the Supporting Information as CIFs embedding the SHELXL-97 res files because of the disordered crystal structure.

According to single crystal X-ray structural analysis, the obtained crystal was obtained as K ₅ [{Ce (H ₂ O) ₇ } ₃ [Na (H ₂ O) -P ₅ W ₃₀ O ₁₁₀ ] · 31H ₂ O (Ce-NaPOM and It was found to be a single crystal. This single crystal belongs to the space group Pnma having a symmetric center, and it was found that a = 28Å, b = 21Å, and c = 20Å.

  13 to 15 are crystal structure diagrams. It is the b-axis projection figure (a) and c-axis projection figure (b) of the crystal | crystallization of FIG. FIG. 14 is an enlarged view of the b-axis projection. FIG. 15 is an enlarged view of the c-axis projection. Some water molecules are omitted.

  In the POM molecule, sodium ions and water molecules were present at an internal stable site at an occupation ratio of 1, respectively. Therefore, it was estimated that ion fluctuation does not occur. In this compound, cerium ions exist as counter cations, and seven crystallization waters coordinate with one cerium ion. The directions of the POM molecules are aligned in one direction, and the cerium ions also form a coordination bond with the terminal oxygen of the POM molecules, thereby cross-linking the POM molecules. The production of the same crystal was repeated. As a result, it was found that crystals having a natural number of 1 to 10 and a natural number of m of 1 to 40 are stable.

<Vacuum heat treatment>
In the vacuum heat treatment, the obtained crystals were vacuum heated at 80 ° C. for 2 hours or 120 ° C. for 4 hours. Thereby, a part or all of the water molecules occupying one ion site in the molecule was removed. In the present specification, the vacuum state means a state in which the vacuum is 10 ⁻⁶ Torr or less.

A crystal obtained by treating the obtained crystal in a vacuum state (10 ⁻⁶ Torr) at 80 ° C. for 2 hours is referred to as Ce-NaPOM (vacuum at 80 ° C. for 2 hours). Also, 120 ° C. The resulting crystals under vacuum (10 ^-6 Torr), referred to those of the process was maintained for 4 hours and Ce-NaPOM (vacuum 120 ° C. 4h treatment).

<IR (temperature dependence measurement of IR spectrum)>
Next, temperature dependence measurement of IR spectrum was performed. In addition, the measurement sample was processed by holding the obtained crystal as it is (Ce-NaPOM (no vacuum heat treatment)) and holding the obtained crystal in a vacuum state (10 ⁻⁶ Torr) at 80 ° C. for 2 hours. (Ce-NaPOM (denoted as vacuum 80 ° C., 2 h treatment)) was used.

  FIG. 16 shows IR spectrum measurement results of a Ce-NaPOM (no vacuum heat treatment) sample and a Ce-NaPOM (vacuum 80 ° C., 2 h treatment) sample. It was almost identical.

FIG. 17 is a graph showing the temperature dependence of the IR spectrum of a Ce-NaPOM (without vacuum heat treatment) sample. After measurement at room temperature (RT: 300K), the temperature was lowered and measurement was performed at each temperature of 250K, 200K, 250K, 200K, 50K, and 10K. At each temperature, none of the three absorption peak positions of 1160, 1070, and 1020 cm ⁻¹ shifted. These peaks are attributed to PO located inside the cavity of the POM molecule. That is, it was found that even if the temperature was lowered from room temperature, the PO expansion and contraction was not affected, and Na did not fluctuate between stable sites even in a high temperature range.

  In the case of Tb, these peak shifts occurred and new peaks appeared. It was speculated that terbium ions that fluctuated between stable sites in the high temperature region slowly stopped at the stable sites in the low temperature region.

<Dielectric constant measurement>
(Example 1-1-1)
FIG. 18 is an apparatus configuration diagram for permittivity measurement. First, pellets (thickness 75 μm, area 0.84 mm ² ) were prepared from powder of the obtained crystals (Ce—NaPOM (without vacuum heat treatment) sample). Next, a gold paste was applied to both sides of the pellet to form an electrode. Next, the electrodes were wired and connected to an Agilent LCR meter (E4980A). Next, voltage-current was applied, and the dielectric constant of a Ce-NaPOM (without vacuum heat treatment) sample was measured by a four-terminal method. The measurement frequency was 3 kHz to 2 MHz, and the applied voltage was 2 V.

  FIG. 19 is a graph showing the temperature dependence of the dielectric loss obtained from the dielectric constant measurement of a Ce-NaPOM (without vacuum heat treatment) sample. In the temperature range of 150K to 300K, no frequency-dependent dielectric loss peak was observed at a frequency of 3 kHz to 2 MHz.

(Example 1-1-2)
Next, a powder of Ce-NaPOM (vacuum treated at 80 ° C. for 2 hours) was used in place of the obtained crystal (Ce-NaPOM (vacuum heat treatment) sample) powder in the same manner as in Test Example 1-1. A pellet was prepared, and the dielectric constant was measured.

  FIG. 20 is a graph showing the temperature dependence of dielectric loss obtained from the dielectric constant measurement of a Ce-NaPOM (vacuum 80 ° C., 2 h treatment) sample. In the temperature range of 150K to 300K, a frequency dependent dielectric loss peak was observed in the range of 270K to 295K at a frequency of 333 Hz to 2 MHz. This was considered to be the peak of dielectric loss accompanying the fluctuation of sodium ions.

<Polarization measurement, PT measurement, PE measurement>
(Example 1-2-1)
Polarization measurements were made. The pyroelectric current was very small and no pyroelectric current peak was observed.

FIG. 21 is an apparatus configuration diagram of PE measurement. First, pellets (thickness: 312 μm, area: 133 mm ² ) were produced from the powder of the obtained crystal (Ce—NaPOM (without vacuum heat treatment) sample). Next, both sides of the pellet were sandwiched between disc-shaped electrodes. Next, it wired to the electrode and connected to PrecisionLC (made by Radiant Technologies). Next, PE (electric field dependence of polarization) of the Ce-NaPOM (no vacuum heat treatment) sample was measured by a Sawyer tower circuit.

(Example 1-2-2)
Next, in the same manner as in Test Example 2-1, except that the powder of the obtained crystal (Ce-NaPOM (without vacuum heat treatment) sample) was replaced with the powder of Ce-NaPOM (vacuum treated at 80 ° C. for 2 hours). A pellet was prepared, and PT measurement and PE measurement were performed.

(Example 1-2-3)
Next, in the same manner as in Test Example 2-1, except that the powder of the obtained crystal (Ce-NaPOM (without vacuum heat treatment) sample) was replaced with the powder of Ce-NaPOM (vacuum treated at 120 ° C. for 4 hours). Then, a pellet was prepared and PE measurement was performed.

  FIG. 22 is a graph showing PT (relationship between integrated value of pyroelectric current and temperature) of a Ce-NaPOM (no vacuum heat treatment) sample and a Ce-NaPOM (vacuum 80 ° C., 2 h treatment) sample. The value of the polarization P could be increased by the vacuum heat treatment.

  FIG. 23 is a graph showing PE of a Ce—NaPOM (without vacuum heat treatment) sample. Almost no dielectric hysteresis was obtained.

  FIG. 24 is a graph showing PE of a Ce—NaPOM (vacuum 80 ° C., 2 h treatment) sample. A certain amount of dielectric hysteresis was obtained. In addition, the dielectric hysteresis increased as the temperature increased from low temperature 250K to room temperature RT (300K).

  FIG. 25 is a graph showing PE of a Ce—NaPOM (vacuum 120 ° C., 4 h treatment) sample. A large dielectric hysteresis was obtained. In addition, the dielectric hysteresis increased as the temperature increased from a low temperature of 260 K to a room temperature RT (300 K). In addition, variation in the data of dielectric hysteresis was also smaller than that of the Ce-NaPOM (vacuum 80 ° C., 2 h treatment) sample.

(Test Example 1)
<Single crystal production>
First, [K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] .15H ₂ O], which is a Preyssler type POM encapsulating sodium ions, was synthesized by a method already reported. Next, 3 ml of H ₂ O was added to 36.6 mg (0.1 mmol) of Tb (NO ₃ ) ₃ .6H ₂ O to prepare a first solution. Next, 12 ml of H ₂ O was added to 1.00 g (0.121 mmol) of K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] · 15H ₂ O to prepare solution B, and the second solution was added to 60 ml. Heated to ° C. Next, the 2nd solution was dripped at the 1st solution, and the 1st mixed solution was prepared.

  Next, the first mixed solution was held at 145 ° C. for 24 hours. Next, 4.00 g (53 mmol) of KCl was added to the solution cooled to room temperature after heating. Thus, a crystal powder was obtained.

  FIG. 26 is a photograph of the obtained crystal. A colorless transparent crystal having a longest diameter of 1 mm was obtained. A molecular complex that included water molecules could not be prepared.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were K ₆ Na ₆ (H ₂ O) _n [Tb ³⁺ -P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as K, Na-TbPOM). It turned out to be. The n and m of this crystal could not be specified.

  The K, Na-TbPOM sample contained a lot of crystal water. As a result, the crystals deteriorated due to dehydration at normal pressure and room temperature.

<Dielectric constant measurement>
Next, pellets were obtained in the same manner as in Example 1-1-1, except that K and Na-TbPOM sample powder were used instead of the obtained crystal (Ce-NaPOM (without vacuum heat treatment) sample) powder. The dielectric constant was measured.

  FIG. 27A is a graph showing the temperature dependence of the dielectric loss obtained from the dielectric constant measurement of the K, Na—TbPOM sample. The dielectric constant was measured at a frequency of 333 Hz to 2 MHz in a temperature range of 150K to 300K. In the frequency range from 333 Hz to 333 kHz, a frequency-dependent dielectric loss peak was observed in the range of 225 to 280K. The peak of this dielectric loss was thought to be due to the fluctuation of terbium ions.

  FIG. 27 (b) is an Arrhenius plot obtained from the temperature dependence of the dielectric loss of the K, Na-TbPOM sample. Each frequency and peak top temperature were used for the calculation. The graph shows the natural logarithm of each frequency on the vertical axis and the reciprocal of the peak top temperature on the horizontal axis. The energy barrier U was 0.487 eV.

<PT measurement>
PT measurement of the K, Na-TbPOM sample was performed using an electrometer (Keithley 6517A). First, the K, Na-TbPOM sample was cooled, and a polling process was performed by applying an electric field of ± 540 V / cm. Next, pyroelectric current was measured while warming at a rate of 0.5 K / min under zero electric field. As a result, a clear pyroelectric current peak was obtained at 250K.

  FIG. 28 is a graph (PT graph) showing the temperature dependence of the value obtained by normalizing the integrated value of the pyroelectric current of the K, Na-TbPOM sample with the integrated value of the pyroelectric current at 100K. The absolute value of polarization started to decrease from 230K and became zero at 320K. This temperature was defined as a ferroelectric development temperature.

<PE measurement>
PE and K of Na-TbPOM sample were measured using Radient Precision LC. FIG. 29 is a dielectric hysteresis loop of the K, Na—TbPOM sample. As the temperature increased to 220K, 250K, and 280K, the dielectric hysteresis increased, and a ferroelectric hysteresis loop was observed when the maximum applied voltage was 350 V / cm at 280K. This temperature coincided with the temperature of the pyroelectric current peak observed by PT measurement. From this, the origin of spontaneous polarization was considered to be due to the bias of terbium ions in the POM molecule.

  From the above, it has been clarified that if a K, Na-TbPOM sample containing water molecules can be prepared, it can be used as a material exhibiting a large dielectric hysteresis by removing the water molecules.

(Comparative Example 1)
<Single crystal production>
First, K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] was dried to a white powder. Next, 1 ml of H ₂ O was added to 100 mg (1.25 × 10 ⁻⁵ mol) of K _12.5 Na _1.5 [NaP ₅ W ₃₀ O ₁₁₀ ] to prepare a fourth solution. Next, a few drops of H ₂ O were added to 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O to prepare a fifth solution. Next, the fourth solution and the fifth solution were mixed to prepare a sixth mixed solution. Next, the sixth mixed solution was heated to reduce the liquid volume to about half, and then allowed to stand to precipitate crystals. Thus, a crystal powder was obtained.

  FIG. 30 is a photograph of the obtained crystal. Transparent crystals with a maximum diameter of 3 mm were obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The X-ray structure analysis, the crystals obtained _{are, NiCl 2 (H 2 O)} n - [Na (H 2 O) P 5 W 30 O 110] · mH 2 O ( abbreviated as (NiCl ₂ -NaPOM). It turned out to be.

(Comparative Example 2)
<Single crystal production>
Comparative Example except that 3.3 mg (1.2 × 10 ⁻⁵ mol) of CrCl ₃ .6H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 31 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 2 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were CrCl ₃ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (CrCl ₃ —NaPOM).) It turned out to be.

(Comparative Example 3)
<Single crystal production>
The same procedure as in Comparative Example 1 was performed except that 2.0 mg (1.5 × 10 ⁻⁵ mol) of CoCl ₂ was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O. Thus, crystal powder was obtained.

  FIG. 32 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 2 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
By X-ray structural analysis, the obtained crystal is CoCl ₂ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (CoCl ₂ —NaPOM).) It turned out to be.

(Comparative Example 4)
<Single crystal production>
Comparative Example except that 2.1 mg (1.2 × 10 ⁻⁵ mol) of CuCl ₂ .2H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 33 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 2 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were obtained as follows: 1CuCl ₂ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (1CuCl ₂ —NaPOM)) It turned out to be.

(Comparative Example 5)
<Single crystal production>
Comparative Example except that 11.1 mg (6.5 × 10 ⁻⁵ mol) of CuCl ₂ .2H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 34 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 1 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were obtained as follows: 5CuCl ₂ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (5CuCl ₂ —NaPOM)) It turned out to be.

(Comparative Example 6)
<Single crystal production>
Comparative Example except that 2.46 mg (1.24 × 10 ⁻⁵ mol) of MnCl ₂ .4H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 35 is a photograph of the obtained crystal. Transparent crystals with a maximum diameter of 3 mm were obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The X-ray structure analysis, the crystals obtained _{are, MnCl 2 (H 2 O)} n - [Na (H 2 O) P 5 W 30 O 110] · mH 2 O ( abbreviated as (MnCl ₂ -NaPOM). It turned out to be.

(Comparative Example 7)
<Single crystal production>
Instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O, 2.00 mg (1.27 × 10 ⁻⁵ mol) of CrCl ₃ was used. Thus, crystal powder was obtained.

  FIG. 36 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 1 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystal obtained by X-ray structural analysis was obtained as VCl ₃ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (VCl ₃ —NaPOM).) It turned out to be.

(Comparative Example 8)
<Single crystal production>
Comparative example except that 2.35 mg (1.18 × 10 ⁻⁵ mol) of FeCl ₂ .4H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 37 is a photograph of the obtained crystal. Pale yellow crystals having a longest diameter of 3 mm were obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were FeCl ₂ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (FeCl ₂ —NaPOM).) It turned out to be.

(Comparative Example 9)
<Single crystal production>
Comparative example except that 2.66 mg (1.28 × 10 ⁻⁵ mol) of FeCl ₃ .6H ₂ O was used instead of 2.9 mg (1.2 × 10 ⁻⁵ mol) of NiCl ₂ .6H ₂ O In the same manner as in Example 1, crystal powder was obtained.

  FIG. 38 is a photograph of the obtained crystal. A transparent crystal having a longest diameter of 1 mm was obtained. When removed from the water, the large crystals cracked immediately.

<X-ray structural analysis>
The crystals obtained by X-ray structural analysis were FeCl ₃ (H ₂ O) _n — [Na (H ₂ O) P ₅ W ₃₀ O ₁₁₀ ] · mH ₂ O (abbreviated as (FeCl ₃ —NaPOM).) It turned out to be.

  N and m of the crystals of Comparative Examples 1 to 9 could not be specified. Table 1 summarizes the composition and characteristics of the crystals obtained.

Molecular metal oxide clusters of the present invention, molecular polarizability is held stably, so also stable structure structurally, has a ferroelectric expression temperature T _C is much higher than that of the monomolecular magnet, a dielectric around room temperature It has the effect of observing hysteresis. The molecular polarization can be stably maintained and the molecular polarization can be easily formed by the molecular polarization forming method to the molecular metal oxide cluster. As a result, it can be applied to increase the density of the ferroelectric memory, and can be a molecular memory. In addition, since it has a stable structure with molecular metal oxide cluster crystals, it can be applied to crystal memories. Moreover, it can also be device-ized as a molecular metal oxide cluster crystal aggregate. It can also be used for nanodevices and nanoelectronic materials that are driven at room temperature. In addition, it can be expected to be applied to actuators and transistors at the molecular level due to the single-molecule and ferroelectric behavior. As described above, the electronic device industry can be used.

DESCRIPTION OF SYMBOLS 10 ... Molecular metal oxide cluster crystal aggregate (pellet), 11 ... Molecular metal oxide cluster crystal, 31 ... Molecular metal oxide cluster, 31c ... Communication hole, 31c1, 31c2 ... Inclusion part.

Claims (18)

  A cluster skeleton having a communication hole and one open end side and the other open end side in the communication hole, each having a clathrate that can clathrate metal ions and water molecules; and A molecular metal oxide cluster comprising metal ions clathrated on one side and water molecules clathrated on the other of the clathrate parts, and having molecular polarization due to the bias of the metal ions.   The molecular metal oxide cluster according to claim 1, wherein the cluster skeleton has a substantially flat spheroid shape, and the communication hole is provided along a rotation axis. The molecular metal oxide cluster according to claim 2, wherein the cluster skeleton is a polyoxometalate represented by a chemical formula P ₅ W ₃₀ O ₁₁₀ . The cluster skeleton is represented by the following chemical formula (1), and in the chemical formula (1), M1 is any metal ion selected from the group of alkali metals and lanthanoids. 2. The molecular metal oxide cluster according to item 1.
M1, H ₂ O-P ₅ W ₃₀ O ₁₁₀ (1) The molecular metal oxide cluster according to claim 4, wherein M1 is any metal ion selected from the group consisting of Na ⁺ , Nd ³⁺ , Dy ^{3+, and} Tb ³⁺ .   A molecular metal oxide cluster crystal according to claim 1, comprising the molecular metal oxide cluster according to claim 1, a counter cation, and a water molecule.   7. The molecular metal oxide cluster crystal according to claim 6, wherein the water molecule includes coordinated crystal water coordinated to a counter cation and non-coordinated crystal water not coordinated to a counter cation.   The molecular metal oxide cluster crystal according to claim 6 or 7, wherein the molecular metal oxide cluster forms an orthorhombic crystal structure.   The molecular metal oxide cluster crystal according to claim 8, comprising a counter cation coordinated with coordinated crystal water and non-coordinated crystal water between lattices of the orthorhombic crystal structure. . In the chemical formula (2), M1 is any metal ion selected from the group of Na ⁺ , Nd ³⁺ , Dy ³⁺ or Tb ³⁺ , and M2 is Na ⁺ , K One, two or more cations selected from the group of ⁺ , Ca ²⁺ , Ce ⁴⁺ or NH ₄ ⁺ , n is a natural number of 1 or more and 10 or less, and m is a natural number of 1 or more and 40 or less. The molecular metal oxide cluster crystal according to any one of claims 6 to 9, wherein:
_{M2, (H 2 O) n} [M1, H 2 O-P 5 W 30 O 110] · mH 2 O ··· (2)   A molecular metal oxide cluster crystal aggregate, wherein the molecular metal oxide cluster crystal according to any one of claims 6 to 10 is aggregated.   The molecular metal oxide cluster crystal aggregate according to claim 11, which is a pellet.   A molecular memory comprising the molecular metal oxide cluster according to any one of claims 1 to 6, wherein the recording unit is a magnitude and direction of molecular polarization in an external electric field 0.   A crystal comprising the molecular metal oxide cluster crystal according to any one of claims 6 to 10, wherein a recording unit is a total magnitude and direction of polarization per mass in an external electric field 0. memory. A molecular property that does not include water molecules by vacuum heating the molecular metal oxide cluster according to any one of claims 1 to 6 to extract inclusion water molecules from the molecular metal oxide cluster to the outside. Forming a metal oxide cluster;
And a step of forming polarization by applying an electric field to the molecular metal oxide cluster that does not include water molecules.   The method for forming molecular polarization on a molecular metal oxide cluster according to claim 15, wherein the vacuum heating is performed at 80 ° C or higher and 140 ° C or lower.   The method according to claim 16, wherein the vacuum heating is performed at 120 ° C or higher.   The method for forming molecular polarization into a molecular metal oxide cluster according to any one of claims 15 to 17, wherein when the electric field is applied, the temperature is raised to near the ferroelectric onset temperature Tc.