1. High-temperature high-pressure synthesized barium-deficient barium dolomite Ba_1-xMg(CO₃)_2-xA method of crystallizing comprising the steps of:

step 1, using analytically pure barium carbonate BaCO₃And analytically pure magnesium oxalate dihydrate MgC₂O₄·2H₂Grinding and mixing O in a molar ratio of (1-x):1 to obtain a mixture as a starting material, wherein the molar ratio of O is 0<x≤0.10；

Step 2, pressing the mixture powder in the step 1 into a cylinder with the diameter of 5 multiplied by 3mm by using a tablet press, plugging a cylindrical sample into a platinum tube with the diameter of 5mm and the thickness of 0.1mm, sealing two ends of the platinum tube by using a welding gun, placing the platinum tube into an h-BN tube, and taking the h-BN as a pressure transmission medium;

step 3, assembling the h-BN pipe provided with the sample in the step 2 in a high-pressure synthesis assembly block and placing the h-BN pipe in a cubic apparatus large press for high-temperature high-pressure reaction;

and 4, after the high-temperature high-pressure reaction is finished, taking out the sample in the step 3, cutting the platinum tube by using a diamond cutter, and naturally air-drying the sample to obtain the barium-containing vacancy barium dolomite crystal.

2. A high temperature high pressure synthetic barium-deficient barium dolomite Ba as claimed in claim 1_1-xMg(CO₃)_2-xThe method for preparing the crystal is characterized in that the method for preparing the h-BN tube in the step 2 is specifically operated as follows: drilling a phi 5mm hole in the center of a phi 10mm h-BN rod on a lathe to form an h-BN tube, inserting a sample into the tube, and sealing two ends of the h-BN tube by using phi 5mm h-BN sheets with the thickness of 2 mm.

3. A high temperature high pressure synthetic barium-deficient barium dolomite Ba as claimed in claim 1_1-xMg(CO₃)_2-xThe method for preparing the crystal is characterized in that the method for assembling the h-BN tube in the high-pressure synthesis assembly block in the step 3 specifically comprises the following operations: selecting a pyrophyllite block, and punching a phi 12mm circular through hole in the center of the pyrophyllite block; a circular graphite heating furnace with the outer diameter of 12mm and the inner diameter of phi 10mm is sleeved in the circular through hole; placing a 10mm h-BN tube sealed sample in the middle of a graphite heating furnace; the upper end and the lower end of the round graphite heating furnace are sealed by pyrophyllite plugs.

4. A high temperature high pressure synthetic barium-deficient barium dolomite Ba as claimed in claim 1_1-xMg(CO₃)_2-xThe method for preparing the crystal is characterized in that the high-temperature high-pressure reaction in the step 3 is divided into two steps: firstly, increasing the pressure to 1GPa, then increasing the temperature to 550 ℃, maintaining the pressure and preserving the heat for 1h, and then quenching; and secondly, increasing the pressure to 3GPa, then increasing the temperature to 850-900 ℃, maintaining the pressure and preserving the heat for 48 hours, and then quenching.

5. A high temperature high pressure synthetic barium-deficient barium dolomite Ba as claimed in claim 1_1-xMg(CO₃)_2-xThe method for preparing the crystal is characterized in that the barium-containing vacancy barium dolomite obtained in the step 4 is the crystal, the size of the crystal is 50-100 mu m, and the requirement of a single crystal X-ray test is met.

6. High-temperature high-pressure synthesized barium-deficient barium dolomite Ba_1-xMg(CO₃)_2-xA crystal characterized in that said barium-containing vacancy barium dolomite Ba_1-xMg(CO₃)_2-xThe crystal structure and symmetry of the phase are three-sided R-3c, and the phase has superlattice and oxygen order and lattice parameters

Background

Bis-carbonate AB (CO)₃)₂The temperature and pressure conditions formed in nature, the ordered crystal structure and its physicochemical properties have been the hot spots of carbonate mineralogy for decades. As a typical bicarbonated mineral, barium dolomite BaMg (CO)₃)₂It is found in succession under different geochemical conditions in nature, and is particularly important for the study of ocean barium-carbon coupling cycle and ocean sediment. The crystal structure of the barium dolomite has two different Ba²⁺And Mg²⁺Cation position and CO₃ ^2-The nature of the ionically linked ordered layered structure results from the limited miscibility of solid solutions, i.e. from Ba²⁺And Mg²⁺A significant difference between the ionic radii. Based on this, Lippmann has proposed BaMg (CO) in 1967₃)₂Can be used as dolomite CaMg (CO)₃)₂The crystal structure and symmetry of the crystalline chemical and geochemical analogs of (a) are determined to be trigonal R-3 m. However, with the increasing accuracy of testing in recent years, BaMg (CO)₃)₂The single crystal X-ray results redefined its crystal structure and found to have superlattice diffraction spots in the inverted space in the c-direction, the presence of the superlattice resulting in the formation of oxygen order and the rotation of the carbonate to form a new crystal structure with double c-axis space group R-3 c. In fact, because of the absence of an oxygen ordered, superlattice in the dolomite crystal structure R-3, the traditional dolomite crystal structure model cannot be used to explain BaMg (CO)₃)₂Medium superlattice and oxygen order formation mechanisms. Furthermore, the naturally found barium dolomite tends to be enriched with radium, which is a radioactive element, but the phenomenon of partial substitution of barium by radium cannot be explained by a simple homogeneous phase. Compared with mineralogy, the view of materials research in materials science holds that materials with oxygen order and superlattice existence generally have the defect of oxygen or extra oxygen in crystal lattices to form new modulation structures. In this case, the barium dolomiteThe existence mechanism of the oxygen order and the superlattice and the evolution of the space group of the superlattice are quantitatively discussed as the oxygen vacancy material, so that a reasonable explanation is hopefully provided for the mineralogical problem, and the traditional dolomite model and the layered ordered dicarbonate crystal structure are more finely modified. However, this has resulted in the failure to perform quantitative crystal structure studies and interpretation of related problems due to the lack of artificially synthesized crystal samples containing the missing barium dolomite.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provides a high-temperature high-pressure synthesized barium-containing vacancy barium dolomite Ba_1-xMg(CO₃)_2-xThe crystal method fills the blank of the research of the barium dolomite as the oxygen vacancy material at present.

The technical scheme of the invention comprises the following steps:

step 1, using analytically pure barium carbonate BaCO₃And analytically pure magnesium oxalate dihydrate MgC₂O₄·2H₂Grinding and mixing O in a molar ratio of (1-x):1 to obtain a mixture as a starting material, wherein the molar ratio of O is 0<x≤0.10；

Step 2, pressing the mixture powder in the step 1 into a cylinder with the diameter of 5 multiplied by 3mm by using a tablet press, plugging a cylindrical sample into a platinum tube with the diameter of 5mm and the thickness of 0.1mm, sealing two ends of the platinum tube by using a welding gun, placing the platinum tube into an h-BN tube, and taking the h-BN as a pressure transmission medium;

step 3, assembling the h-BN pipe provided with the sample in the step 2 in a high-pressure synthesis assembly block and placing the h-BN pipe in a cubic apparatus large press for high-temperature high-pressure reaction;

and 4, after the high-temperature high-pressure reaction is finished, taking out the sample in the step 3, cutting the platinum tube by using a diamond cutter, and naturally air-drying the sample to obtain the barium-containing vacancy barium dolomite crystal.

The manufacturing method of the h-BN pipe in the step 2 is specifically operated as follows: drilling a phi 5mm hole in the center of a phi 10mm h-BN rod on a lathe to form an h-BN tube, inserting a sample into the tube, and sealing two ends of the h-BN tube by using phi 5mm h-BN sheets with the thickness of 2 mm.

The method for assembling the h-BN pipe in the high-pressure synthesis assembly block in the step 3 specifically comprises the following operations: selecting a pyrophyllite block, and punching a phi 12mm circular through hole in the center of the pyrophyllite block; a circular graphite heating furnace with the outer diameter of 12mm and the inner diameter of phi 10mm is sleeved in the circular through hole; placing a 10mm h-BN tube sealed sample in the middle of a graphite heating furnace; the upper end and the lower end of the round graphite heating furnace are sealed by pyrophyllite plugs.

Wherein, the high-temperature high-pressure reaction in the step 3 comprises two steps: firstly, increasing the pressure to 1GPa, then increasing the temperature to 550 ℃, maintaining the pressure and preserving the heat for 1h, and then quenching; and secondly, increasing the pressure to 3GPa, then increasing the temperature to 850-900 ℃, maintaining the pressure and preserving the heat for 48 hours, and then quenching.

Wherein, when x is 0, the synthetic product obtained in the step 4 is barium dolomite BaMg (CO) without vacancy₃)₂Phase (1); when 0 is present<x is less than or equal to 0.10 is a single phase, i.e. barium-deficient barium dolomite Ba_1-xMg(CO₃)_2-xA crystal having a maximum barium defect level of 10%; when x is more than or equal to 0.15, a mixed phase appears, namely MgCO and magnesite with barium deficiency₃A mixture of (a).

Wherein the barium-containing vacancy barium dolomite obtained in the step 4 is a crystal, the size of the crystal is 50-100 mu m, and the requirement of a single crystal X-ray test is met.

Wherein, the synthetic product obtained in the step 4 is barium dolomite BaMg (CO) without defect₃)₂The crystal structure and space group of the phase are three-side structures R-3m, no superlattice and oxygen order are generated, and lattice parameters are Barium-containing vacancy barium dolomite Ba_1-xMg(CO₃)_2-xThe crystal structure and space group of the phase are three-side structure R-3c, and the phase has superlattice, oxygen order and lattice parameter

The invention has the advantages that:

in 1961, barium dolomite was first discovered in Green River Format in Wyoming, USA, and then widely observed throughout the world. Mineralogical studies have shown that the crystal structure of the barium dolomite is completely different from that of the calcite type and that of the dolomite type, due to the Ba²⁺Radius of ionBiMg²⁺Is/are as followsMuch larger, form huge BaO in the crystal lattice₁₂Twelve ligands make the crystal structure and space group symmetry of the blanc fixe controversial for a long time, especially the crystal structure observes that the characteristics of oxygen order and superlattice can not be explained by the traditional dolomite lamellar model, and meanwhile, the natural blanc fixe is enriched with radium at the barium positionAlso, the root cause of (a) cannot be reasonably explained from its complex crystal structure. Based on the above, the invention finds the difficult problems which are not solved in the mineralogy research in about half century from the blanc fixe, and has the innovation points that the viewpoint of oxygen vacancy material is introduced into the mineralogy, the vacancy in the crystal structure is quantitatively researched and the mechanism is explained by artificially synthesizing the barium vacancy blanc fixe crystal, and relevant boundary conditions are given, and the beneficial effects are as follows:

1. reasonable explanations are given for the superlattice and oxygen ordering observed in barium dolomite. According to the crystal structure of the vacancy barium dolomite, the vacancy-free barium dolomite BaMg (CO)₃)₂The crystal structure and symmetry of the phase are three-way R-3m, and no superlattice and oxygen order exist; barium-containing vacancy barium dolomite Ba_1-xMg(CO₃)_2-xThe crystal structure and symmetry of the phase are trigonal R-3c, having a superlatticeLattice and oxygen are ordered. The results show that Ba²⁺The absence of sites results in anionic CO₃ ^2-Cause an originally rigid CO₃ ^2-Around [001 ]]The direction is obviously rotated, so that the topological relation of the arrangement of oxygen atoms is changed, and a superlattice and oxygen order are formed. Further, Ba²⁺The root cause of the position defect is the huge BaO₁₂Dodecaligand and smaller MgO₆The hexa-ligands have a very large size difference and when they form an alternating layered structure in the lattice, there is a strong mismatch between adjacent layers. In this case, Ba²⁺The vacancy generated by the position can effectively reduce mismatching between adjacent layers and relieve local lattice stress, so that barium vacancy, superlattice and oxygen ordering in the barium dolomite are the results of spontaneous induction of crystal lattices. In comparison, Ca²⁺Radius ofAnd Mg²⁺Radius ofWith a small difference, CaO₆Hexaligand and MgO₆The hexa-ligand is capable of forming a matched dolomite layered structure, Ca²⁺The position can not generate a defect position and can not cause CO₃ ^2-And thus no superlattice and oxygen ordering can be observed in the dolomite structure. Furthermore, according to the experimental results, the maximum number of missing sites that the barium dolomite barium site can accommodate is 10%.

2. Reasonable explanation is given to the reason that the barium position in the natural barium dolomite is enriched with radium. Although Ba²⁺Site-generated vacancy is the result of spontaneous induction of the barium dolomite lattice, but the chemical stability of the barium vacancy lattice is relatively poor compared to a fully occupied lattice. Based on this, radium with smaller radiusFilling the defect sites of the barium position can not only relieve the lattice stress, but also increase the chemical stability, which explains the natural bariumThe reason why dolomite can enrich radium at barium sites. Based on the principle, the barium-deficient blanc fixe related to the invention can be applied to the extraction and separation of radioactive radium elements.

Detailed Description

Example 1:

high-temperature high-pressure synthesized barium-deficient barium dolomite Ba_0.95Mg(CO₃)_1.95A process for the formation of 0.05 crystals, comprising the steps of:

step 1, using analytically pure barium carbonate BaCO₃And analytically pure magnesium oxalate dihydrate MgC₂O₄·2H₂Grinding and uniformly mixing O with the molar ratio of 0.95:1 as a starting material

Step 2, pressing the mixture powder in the step 1 into a cylinder with the diameter of 5 multiplied by 3mm by using a tablet press, plugging a cylindrical sample into a platinum tube with the diameter of 5mm and the thickness of 0.1mm, sealing two ends of the platinum tube by using a welding gun, placing the platinum tube into an h-BN tube, and taking the h-BN as a pressure transmission medium;

step 3, assembling the h-BN pipe provided with the sample in the step 2 in a high-pressure synthesis assembly block and placing the h-BN pipe in a cubic apparatus large press for high-temperature high-pressure reaction;

step 4, after the high-temperature high-pressure reaction is finished, taking out the sample in the step 3, cutting the platinum tube by using a diamond cutter, and naturally air-drying the sample to obtain barium-containing barium-deficient barite dolomite Ba_0.95Mg(CO₃)_1.95And (4) crystals.

The manufacturing method of the h-BN pipe in the step 2 is specifically operated as follows: drilling a phi 5mm hole in the center of a phi 10mm h-BN rod on a lathe to form an h-BN tube, inserting a sample into the tube, and sealing two ends of the h-BN tube by using phi 5mm h-BN sheets with the thickness of 2 mm.

The method for assembling the h-BN pipe in the high-pressure synthesis assembly block in the step 3 specifically comprises the following operations:

3.1, selecting a pyrophyllite block, and punching a circular through hole with the diameter of phi 12mm in the center of the pyrophyllite block;

3.2, sleeving a circular graphite heating furnace with the outer diameter of 12mm and the inner diameter phi of 10mm in the circular through hole;

3.3, placing a 10mm h-BN tube sealed sample in the middle of a graphite heating furnace;

and 3.4, sealing the upper end and the lower end of the round graphite heating furnace by pyrophyllite plugs.

Wherein, the high-temperature high-pressure reaction in the step 3 comprises two steps: step one, increasing the pressure to 1GPa, then increasing the temperature to 550 ℃, maintaining the pressure and preserving the heat for 1h, and then quenching; and secondly, increasing the pressure to 3GPa, then increasing the temperature to 850 ℃, maintaining the pressure and preserving the heat for 48 hours, and then quenching.

The obtained barium-containing vacancy barium dolomite is a crystal, the size of the crystal is 50-100 mu m, and the requirement of a single crystal X-ray test is met. The barium-containing vacancy barium dolomite Ba_0.95Mg(CO₃)_1.95The crystal structure and symmetry of the phase are three-sided R-3c, and the phase has superlattice and oxygen order and lattice parameters

Example 2:

high-temperature high-pressure synthesized barium-deficient barium dolomite Ba_0.90Mg(CO₃)_1.90A process for the formation of 0.1 crystal, comprising the steps of:

step 1, using analytically pure barium carbonate BaCO₃And analytically pure magnesium oxalate dihydrate MgC₂O₄·2H₂Grinding and uniformly mixing O in a molar ratio of 0.90:1 to serve as an initial raw material;

step 2, pressing the mixture powder in the step 1 into a cylinder with the diameter of 5 multiplied by 3mm by using a tablet press, plugging a cylindrical sample into a platinum tube with the diameter of 5mm and the thickness of 0.1mm, sealing two ends of the platinum tube by using a welding gun, placing the platinum tube into an h-BN tube, and taking the h-BN as a pressure transmission medium;

step 3, assembling the h-BN pipe provided with the sample in the step 2 in a high-pressure synthesis assembly block and placing the h-BN pipe in a cubic apparatus large press for high-temperature high-pressure reaction;

step 4, after the high-temperature high-pressure reaction is finished, taking out the sample in the step 3, cutting the platinum tube by using a diamond cutter, naturally drying the sample,to obtain barium-containing barium-deficient barium dolomite Ba_0.90Mg(CO₃)_1.90And (4) crystals.

The manufacturing method of the h-BN pipe in the step 2 is specifically operated as follows: drilling a phi 5mm hole in the center of a phi 10mm h-BN rod on a lathe to form an h-BN tube, inserting a sample into the tube, and sealing two ends of the h-BN tube by using phi 5mm h-BN sheets with the thickness of 2 mm.

The method for assembling the h-BN pipe in the high-pressure synthesis assembly block in the step 3 specifically comprises the following operations:

3.1, selecting a pyrophyllite block, and punching a circular through hole with the diameter of phi 12mm in the center of the pyrophyllite block;

3.2, sleeving a circular graphite heating furnace with the outer diameter of 12mm and the inner diameter phi of 10mm in the circular through hole;

3.3, placing a 10mm h-BN tube sealed sample in the middle of a graphite heating furnace;

and 3.4, sealing the upper end and the lower end of the round graphite heating furnace by pyrophyllite plugs.

Wherein, the high-temperature high-pressure reaction in the step 3 comprises two steps: step one, increasing the pressure to 1GPa, then increasing the temperature to 550 ℃, maintaining the pressure and preserving the heat for 1h, and then quenching; and secondly, boosting the pressure to 3GPa, then raising the temperature to 900 ℃, maintaining the pressure and preserving the heat for 48 hours, and then quenching.

The obtained barium-containing vacancy barium dolomite is a crystal, the size of the crystal is 50-100 mu m, and the requirement of a single crystal X-ray test is met. The barium-containing vacancy barium dolomite Ba_0.90Mg(CO₃)_1.90The crystal structure and symmetry of the phase are three-sided R-3c, and the phase has superlattice and oxygen order and lattice parameters

Comparative example 1

High-temperature high-pressure synthesized barium-deficient barium dolomite Ba_0.85Mg(CO₃)_1.85The method for preparing the crystal, wherein x is 0.15, comprises the following steps:

step (ii) of1. Using analytically pure barium carbonate BaCO₃And analytically pure magnesium oxalate dihydrate MgC₂O₄·2H₂Grinding and uniformly mixing O in a molar ratio of 0.85:1 to serve as a starting material;

step 2, pressing the mixture powder in the step 1 into a cylinder with the diameter of 5 multiplied by 3mm by using a tablet press, plugging a cylindrical sample into a platinum tube with the diameter of 5mm and the thickness of 0.1mm, sealing two ends of the platinum tube by using a welding gun, placing the platinum tube into an h-BN tube, and taking the h-BN as a pressure transmission medium;

step 3, assembling the h-BN pipe provided with the sample in the step 2 in a high-pressure synthesis assembly block and placing the h-BN pipe in a cubic apparatus large press for high-temperature high-pressure reaction;

and 4, after the high-temperature high-pressure reaction is finished, taking out the sample in the step 3, cutting the platinum tube by using a diamond cutter, and naturally air-drying the sample to obtain the mixture of barium-deficient barium dolomite crystals and magnesite crystals.

The manufacturing method of the h-BN pipe in the step 2 is the same, and the specific operation is as follows: drilling a phi 5mm hole in the center of a phi 10mm h-BN rod on a lathe to form an h-BN tube, inserting a sample into the tube, and sealing two ends of the h-BN tube by using phi 5mm h-BN sheets with the thickness of 2 mm.

The method for assembling the h-BN pipe in the high-pressure synthesis assembly block in the step 3 is the same, and the specific operations comprise:

3.1, selecting a pyrophyllite block, and punching a circular through hole with the diameter of phi 12mm in the center of the pyrophyllite block;

3.2, sleeving a circular graphite heating furnace with the outer diameter of 12mm and the inner diameter phi of 10mm in the circular through hole;

3.3, placing a 10mm h-BN tube sealed sample in the middle of a graphite heating furnace;

and 3.4, sealing the upper end and the lower end of the round graphite heating furnace by pyrophyllite plugs.

Wherein, the high-temperature high-pressure reaction in the step 3 comprises two steps: step one, increasing the pressure to 1GPa, then increasing the temperature to 550 ℃, maintaining the pressure and preserving the heat for 1h, and then quenching; and secondly, boosting the pressure to 3GPa, then raising the temperature to 900 ℃, maintaining the pressure and preserving the heat for 48 hours, and then quenching.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.