CN112663142B - Ruddlesden-Popper type manganese oxide single crystal and preparation method thereof - Google Patents

Ruddlesden-Popper type manganese oxide single crystal and preparation method thereof Download PDF

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CN112663142B
CN112663142B CN202011415856.7A CN202011415856A CN112663142B CN 112663142 B CN112663142 B CN 112663142B CN 202011415856 A CN202011415856 A CN 202011415856A CN 112663142 B CN112663142 B CN 112663142B
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manganese oxide
type manganese
ruddlesden
single crystal
popper
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CN112663142A (en
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吴枚霞
梁锡辉
王君君
胡金花
黄钦
许平
王巧
林丹
陈志涛
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Institute of Semiconductors of Guangdong Academy of Sciences
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Abstract

The invention discloses a Ruddlesden-Popper (RP for short) type manganese oxide single crystal and a preparation method thereof, wherein the preparation method comprises the following steps: step S1, preparing strip-shaped RP type manganese oxide polycrystalline material rods; and step S2, placing the seed crystal and the strip-shaped polycrystalline material rod of the RP-type manganese oxide in a floating zone melting furnace, and crystallizing at the end of the seed crystal by taking laser as a heating source to obtain the single crystal of the RP-type manganese oxide. Because the laser is used as a heating source, local rapid heating of seed crystals and strip-shaped RP-type manganese oxide polycrystalline material rods can be realized; and because the laser heating has larger temperature gradient and more uniform temperature distribution, the possibility of generating undercooling is reduced, the stability of a melting zone and the whole growth process is ensured, and the preparation of the large-size RP type manganese oxide single crystal is possible.

Description

Ruddlesden-Popper type manganese oxide single crystal and preparation method thereof
Technical Field
The invention relates to a preparation method of Ruddlesden-Popper type single crystal, in particular to Ruddlesden-Popper type manganese oxide single crystal and a preparation method thereof.
Background
Perovskite manganese oxides have attracted much attention and research due to their Colossal Magneto-Resistance effect (CMR). Research has found that the layered perovskite manganese oxide exhibits strong anisotropy in magnetic and transport, resulting in different physical properties compared to three-dimensional perovskites. Wherein, the chemical formula is An+ 1MnnO3n+1The Ruddlesden-Popper type manganese oxide (RP type manganese oxide for short) formed by alternately arranging the perovskite layer and the rock salt layer changes the magnetism and the transport property of the material to a certain extent because the introduction of the rock salt layer increases the quantity of bridge oxygen in an exchange path along a z-axis, provides a precious experimental model for researching the influence of the magnetic lattice size on the giant magnetoresistance effect, and becomes a typical layered perovskite material.
However, the preparation difficulty of the existing large-size RP-type manganese oxide single crystal is higher, and particularly the preparation of the single crystal with the chemical general formula A is difficultn+1MnnO3n+1(wherein n is 1 or 3, and the A site is calcium ion). For example, although an RP type manganese oxide single crystal with n ═ 1 can be produced by a molten salt method, the size of the single crystal produced is small, and usually less than 1 mm.
Disclosure of Invention
In order to solve the problem that the large-size Ruddlesden-Popper type manganese oxide single crystal is difficult to prepare, through a great deal of research and experiments, the inventor finds that the large-size Ruddlesden-Popper type manganese oxide single crystal can be prepared by heating a strip-shaped Ruddlesden-Popper type manganese oxide polycrystalline material rod by adopting laser as a heating source in a floating zone melting furnace.
To this end, according to an aspect of the present invention, there is provided a method for preparing a Ruddlesden-Popper type manganese oxide single crystal, the method comprising the steps of:
step S1: preparing strip Ruddlesden-Popper type manganese oxide polycrystalline material rods;
step S2: and placing the seed crystal and the strip Ruddlesden-Popper type manganese oxide polycrystalline material rod in a floating zone melting furnace, and crystallizing at the end of the seed crystal by using laser as a heating source to obtain Ruddlesden-Popper type manganese oxide single crystal.
According to the technical scheme, the laser with good focusing performance is used as a heating source, so that local rapid heating of seed crystals and strip Ruddlesden-Popper type manganese oxide polycrystalline material rods can be realized; and because the laser heating has larger temperature gradient and more uniform temperature distribution, the possibility of generating component supercooling is reduced, and the stability of a melting zone and the whole growth process is ensured, therefore, the technical scheme provided by the embodiment of the invention enables the preparation of the large-size Ruddlesden-Popper (RP for short) type manganese oxide single crystal to be possible.
In some embodiments, the seed crystal in the embodiments of the present invention may be single crystal or polycrystalline.
In some embodiments, in obtaining the RP type manganese oxide single crystal, the seed crystal and the strip-shaped RP type manganese oxide polycrystalline ingot are rotated in opposite directions relative to each other and moved in the same direction and at the same rate relative to the laser heat source. Therefore, the stable growth of the RP-type manganese oxide single crystal at the seed crystal end can be ensured, and the quality of the RP-type manganese oxide single crystal grown at the seed crystal end can be further ensured.
In some embodiments, the growth conditions of the RP type manganese oxide single crystal are set as follows: the strip-shaped RP type manganese oxide polycrystalline material rod rotates at the rotating speed of 15r/min-30 r/min; the seed crystal rotates at the rotating speed of 20r/min-30 r/min; the growth speed of the RP type manganese oxide single crystal is 2mm/h-6 mm/h; the heating power of the laser for growing the RP type manganese oxide single crystal is 200W-300W; the oxygen pressure in the floating zone melting furnace is 0.6MPa-0.87 MPa. The rotating speed of the strip-shaped RP-type manganese oxide polycrystalline material rod is set to be 15r/min-30r/min, and the rotating speed of the seed crystal is set to be 20r/min-30r/min, so that the full diffusion of atoms and the stable growth of the single crystal are facilitated, high-quality single crystals with uniform components and few defects can be obtained, and the polycrystalline structure grown on the seed crystal due to the fact that the rotating speed of the strip-shaped RP-type manganese oxide polycrystalline material rod is too high or too low relative to the rotating speed of the seed crystal can be avoided; and the inventor determines the growth speed of the single crystal matched with the laser as the heating source through a large amount of calculation and experiments, so that the growth speed of the RP-type manganese oxide single crystal is set to be 2-6 mm/h, and the strip-shaped RP-type manganese oxide polycrystalline material rod can stably grow the single crystal on the seed crystal under the heating of the laser. In addition, the RP type manganese oxide single crystal is produced in an environment where the oxygen pressure is high, and oxygen vacancies in the RP type manganese oxide single crystal can also be reduced.
Generally, the higher the power of the floating zone melting furnace generating the laser, and the smaller the spot diameter, the higher the power density and the stronger the local heating capacity. However, it is also considered that when the power of the floating zone melting furnace is too large, the irradiation effect of the laser can be shielded by remote atmospheric disturbance, thermal disturbance and close-range material evaporation. In consideration of the above factors, the embodiment of the invention preferably selects the floating zone melting furnace with the power of 800W-1200W. Particularly preferably, the floating zone melting furnace with the power of 1000W is selected, at the moment, only 20% -30% of heating power of the floating zone melting furnace is needed, the preparation effect of the RP type manganese oxide single crystal can be ensured, the heating power of the floating zone melting furnace is convenient to control, and moreover, because the heating power of the floating zone melting furnace is not high, the loss of the floating zone melting furnace can be reduced, and the service life of the floating zone melting furnace is prolonged.
In some embodiments, the strip-shaped polycrystalline rod of RP-type manganese oxide is prepared by:
step S11: repeatedly calcining and processing the ground and mixed raw materials to obtain RP type manganese oxide polycrystalline powder;
step S12: and pressing the RP type manganese oxide polycrystalline powder into strip-shaped material rods and then calcining to obtain the strip-shaped RP type manganese oxide polycrystalline material rods. The strip-shaped RP-type manganese oxide polycrystalline material rod is obtained by calcining the strip-shaped material rod formed by pressing the RP-type manganese oxide polycrystalline powder, so that the grain structure of the prepared strip-shaped RP-type manganese oxide polycrystalline material rod can be ensured to be more uniform.
In some embodiments, the calcination processing includes the sequential steps of press forming, calcining, crushing, and grinding, wherein the calcination process in the calcination processing is performed under the temperature condition that the temperature of each calcination is higher than that of the previous calcination, and the calcination temperature of the pressed bar-shaped material rod in the step S12 is the same as that of the calcination process in the last calcination processing. The RP type manganese oxide polycrystalline powder is prepared by repeated calcination processing, the calcination processing comprises the process steps of press forming, calcination, crushing and grinding mixing, and the calcination process in the calcination processing has the temperature condition that the temperature of each calcination is higher than that of the previous calcination, and meanwhile, the calcination temperature of the prepared strip-shaped RP type manganese oxide polycrystalline material rod is the same as that of the calcination process in the last calcination processing, so that the crystal grains of the prepared strip-shaped RP type manganese oxide polycrystalline material rod are large enough, and the strip-shaped RP type manganese oxide polycrystalline material rod with large crystal grains can be rapidly grown into RP type manganese oxide single crystals when being heated by a floating zone melting furnace; due to the adoption of laser heating, the stability of a melting zone and the whole growth process is ensured by the larger temperature gradient and the more uniform temperature distribution of the laser heating, so that the RP type manganese oxide single crystal with larger size can be prepared.
In some embodiments, the chemical composition formula of the prepared RP-type manganese oxide single crystal is An+1MnnO3n+1Wherein, A is calcium ion, n is 1 or 3; repeatedly calcining and processing the ground and mixed raw materials to obtain the RP-type manganese oxide polycrystalline powder, which comprises the following steps:
step S111: pressing the mixed manganese oxide raw material powder into a first block, primarily calcining for 8-12 h at 900-1000 ℃, crushing, grinding and mixing, and pressing into a second block;
step S112: calcining the second block for 8-12 h at 1100-1200 ℃, crushing, grinding, mixing and pressing into a third block;
step S113: calcining the third block body for 8-10 h at 1300-1380 ℃, crushing the calcined third block body, and grinding into powder to obtain RP-type manganese oxide polycrystalline powder; in the step S12, the condition for calcining the bar-shaped material rod is that the bar-shaped material rod is calcined for 8 to 10 hours at 1300 to 1380 ℃. This enables the production of a pure-phase polycrystalline powder of RP-type manganese oxide and the production ofThe preparation chemical composition formula is An+1MnnO3n+1Wherein A is calcium ion and n is 1 or 3, and a single crystal of RP-type manganese oxide. Ca due to n ═ 1 or 3n+1MnnO3n+1The structure can be seen as that the perovskite layer and the rock salt layer are alternately arranged, the quantity of bridge oxygen in an exchange path along the z axis is increased through the introduction of the rock salt layer, the magnetism and the transport property of the systems are changed to a certain extent, compared with the traditional perovskite structure, the RP type manganese oxide single crystal has excellent high-temperature chemical stability and thermal stability, and the material has good oxygen ion conductivity.
In some embodiments, the temperature ramp rate for all calcination processes is from 180 ℃/h to 220 ℃/h; the temperature reduction rate of the calcination process in the step S12 is 80 ℃/h-120 ℃/h. Therefore, sufficient calcination time is ensured in each calcination process, and the strip-shaped RP-type manganese oxide polycrystalline material rod is ensured to be finally formed through a slower cooling speed.
In some embodiments, the crystal structure of the RP-type manganese oxide single crystal is a layered perovskite structure, the space group of which is I41And/acd (n ═ 1) and Pbca (n ═ 3).
In some embodiments, in step S11: the raw materials are calcium carbonate and manganese dioxide according to a chemical composition general formula Can+1MnnO3n+1(wherein n is 1 or 3), fully grinding and uniformly mixing to obtain the product. For example, when n is 1, CaCO3And MnO with MnO2The molar ratio of (A) to (B) is 2: 1; when n is 3, CaCO3And MnO with MnO2The molar ratio of (A) to (B) is 4: 3. The invention adopts laser to component ratio according to the chemical composition general formula Can+1MnnO3n+1(wherein n is 1 or 3) heating the strip-shaped RP-type manganese oxide polycrystalline material rod to ensure that the strip-shaped RP-type manganese oxide polycrystalline material rod can grow into Ca with single phase at the seed crystal end according to the mixture ration+1MnnO3n+1。
According to another aspect of the present invention, there is provided an RP type manganese oxide single crystal produced by the aforementioned production method. Thus, the obtained RP-type manganese oxide single crystal has the characteristics of large size and single structure compared with the common RP-type manganese oxide single crystal.
The method uses laser with better focusing property as a heating source, and obtains the RP-type manganese oxide single crystal by moving the seed crystal and the strip-shaped RP-type manganese oxide polycrystalline material rod in the same direction and at the same speed and crystallizing at the seed crystal end; and because the laser can realize local rapid heating, the laser has larger temperature gradient and more uniform temperature distribution, the possibility of component supercooling is reduced, the stability of a melting zone and the whole growth process is ensured, the growth stability of the RP-type manganese oxide single crystal is improved, and the large-size RP-type manganese oxide single crystal can be prepared.
Drawings
FIG. 1 is a process flow chart of a method for producing an RP type manganese oxide single crystal according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating the detailed process of step S1 in the method shown in FIG. 1;
FIG. 3 is a flowchart illustrating the detailed process of step S11 in the method shown in FIG. 2;
FIG. 4 is Can+1MnnO3n+1An XRD pattern of (n ═ 1) powder and an XRD pattern of RP type manganese oxide single crystal;
FIG. 5 is Can+1MnnO3n+1XRD pattern of (n ═ 3) powder;
FIG. 6, panel a, shows the preparation of Ca by infrared float zone meltingn+1MnnO3n+1Optical photograph of (n ═ 1) single crystal, and graph b in fig. 6 shows Ca produced by laser float zone melting methodn+1MnnO3n+1Optical photograph of (n-1) RP type manganese oxide single crystal, and graph c in fig. 6 shows Ca produced by laser float zone melting methodn+1MnnO3n+1An ingot photograph of (n ═ 1) RP type manganese oxide single crystal;
FIG. 7A shows Ca produced by laser float zone meltingn+1MnnO3n+1(n-3) optical photograph of RP type manganese oxide single crystal, and graph b in fig. 7 shows Ca prepared by laser float zone melting methodn+1MnnO3n+1Ingot photographs of (n ═ 3) RP type manganese oxide single crystals.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term "comprising", without further limitation, means that the element so defined is not excluded from the group of processes, methods, articles, or devices that include the element.
The present invention will be described in further detail with reference to the accompanying drawings.
FIG. 1 schematically shows a method for producing an RP type manganese oxide single crystal according to an embodiment of the present invention, which makes it possible to produce a large-sized RP type manganese oxide single crystal by producing a strip-shaped polycrystalline rod of RP type manganese oxide and using a laser as a heating source, as shown in FIG. 1, the method comprising the steps of:
step S1: preparing a strip-shaped RP type manganese oxide polycrystalline material rod;
step S2: and placing the seed crystal and the strip-shaped polycrystalline material rod of the RP-type manganese oxide in a floating zone melting furnace, and crystallizing at the end of the seed crystal by using laser as a heating source to obtain the single crystal of the RP-type manganese oxide.
Wherein, in step S1, as a preferred example, a strip-shaped RP-type manganese oxide polycrystalline rod may be prepared by first preparing an RP-type manganese oxide polycrystalline powder, and fig. 2 exemplarily shows an embodiment of a method of preparing a strip-shaped RP-type manganese oxide polycrystalline rod, as shown in fig. 2, which includes the steps of:
step S11: repeatedly calcining and processing the ground and mixed raw materials to obtain RP type manganese oxide polycrystalline powder;
step S12: and pressing the RP type manganese oxide polycrystalline powder into strip-shaped material rods, and calcining to obtain the strip-shaped RP type manganese oxide polycrystalline material rods.
Specifically, in step S11, the calcination processing treatment may be implemented as process steps including press forming, calcination, crushing, and grinding mixing, which are sequentially performed in the order of press forming, calcination, crushing, and grinding mixing, and wherein the calcination process is performed under a temperature condition that the temperature of each calcination is higher than that of the previous calcination. In step S12, when the pressed bar-shaped charge bar is calcined, it is preferable that the calcination temperature is set to be the same as the last calcination temperature in step S11. The last calcination temperature in step S11 is the temperature of the calcination process in the last calcination processing in step S11, that is, the one-time calcination process for preparing the RP-type manganese oxide polycrystalline powder after the one-time calcination.
Illustratively, fig. 3 shows a method for preparing an RP-type manganese oxide polycrystalline powder according to an embodiment of the present invention, and referring to fig. 3, the RP-type manganese oxide polycrystalline powder may be prepared by the following steps:
step S111: pressing the mixed manganese oxide raw material powder into a first block, primarily calcining for 8-12 h at 900-1000 ℃, crushing, grinding and mixing, and pressing into a second block:
step S112: calcining the second block for 8-12 h at 1100-1200 ℃, crushing, grinding, mixing and pressing into a third block;
step S113: and (3) calcining the third block body for 8-10 h at 1300-1380 ℃ for three times at the heating rate of 180-220 ℃/h, crushing the calcined third block body, and grinding into powder to obtain the RP-type manganese oxide polycrystalline powder.
Preferably, in cooperation with the embodiment shown in fig. 3, the prepared RP-type manganese oxide polycrystalline powder is pressed into a strip-shaped material rod, and then calcined at 1300-1380 ℃ for 8-10 h, wherein the temperature rise rate in the calcination process is set to 180-220 ℃/h, and the temperature drop rate is set to 80-120 ℃/h, so that the strip-shaped RP-type manganese oxide polycrystalline material rod is obtained through calcination.
As a preferred implementation example, in step S2, the seed crystal and the strip-shaped RP type manganese oxide polycrystalline ingot are placed in a float zone melting furnace with laser as a heating source to crystallize at the seed end to obtain an RP type manganese oxide single crystal, and the seed crystal and the strip-shaped RP type manganese oxide polycrystalline ingot are further arranged to rotate in opposite directions relative to each other and to move in the same direction and at the same rate relative to the laser heating source with the heating source fixed. Illustratively, the growth conditions of the RP type manganese oxide single crystal are set as follows: the rotating speed of the strip-shaped RP type manganese oxide polycrystalline material rod is vMultiple purposeRotating at a rotating speed of 15r/min-30 r/min; the rotation speed of the seed crystal is vSeed of cornRotating at a rotating speed of 20r/min-30 r/min; the rotating directions of the strip-shaped RP-type manganese oxide polycrystalline material rod and the seed crystal are opposite; the growth speed of the RP type manganese oxide single crystal is set to be 2mm/h-6 mm/h; the heating power of the laser for growing the RP type manganese oxide single crystal is 200W-300W; the oxygen pressure in the floating zone melting furnace is 0.6MPa-0.87 MPa.
In specific application, the preparation method of the RP type manganese oxide single crystal can be utilized to prepare the single crystal with the chemical composition general formula of Can+1MnnO3n+1N-1 or 3, wherein the crystal structure of the prepared RP-type manganese oxide single crystal is a layered perovskite structure, and the space group is I41And/acd (n ═ 1) and Pbca (n ═ 3). The following will be prepared by the chemical formula An+1MnnO3n+1An RP type manganese oxide single crystal with n ═ 1 or 3 is taken as an example, and a production method thereof is exemplified with reference to specific examples.
Example 1
Chemical formula is Can+1MnnO3n+1The method for preparing an RP type manganese oxide single crystal of (n ═ 1) includes the steps of:
the first step is as follows: mixing CaCO3And MnO2Is represented by the chemical formula Can+1MnnO3n+1(n-1) in a stoichiometric ratio, CaCO3And MnO with MnO2The molar ratio of (A) to (B) is 2: 1. For example, weighing CaCO310.009g of starting material and MnO24.347g of raw material.
The weighed raw materials are placed in an agate mortar and ground for 1 hour, so that the raw materials are ground and uniformly mixed.
Pressing the mixed raw materials into a first block, carrying out primary calcination for 8 hours at the temperature of 900 ℃, taking out the first block subjected to primary calcination, crushing, grinding and mixing the first block, then pressing the first block into a second block, carrying out secondary calcination for 10 hours at the temperature of 1100 ℃, crushing, grinding and mixing the second block subjected to secondary calcination again, then pressing the second block into a third block, carrying out tertiary calcination for 8 hours at the temperature of 1320 ℃, grinding and mixing the third block subjected to tertiary calcination, and then pressing the third block into manganese oxide strip bars, wherein the heating rate of all the calcination processes is 200 ℃ per hour.
The second step is that: and calcining the manganese oxide strip material rod at the temperature of 1320 ℃ for 8 hours to prepare the strip RP type manganese oxide polycrystalline material rod, wherein the calcining heating rate is 200 ℃ per hour, and the cooling rate is 100 ℃ per hour.
The third step: putting seed crystals and calcined strip-shaped RP-type manganese oxide polycrystalline material rods into a floating zone melting furnace, adopting laser as a heating source, melting and butting the end parts of the seed crystals and one end of each strip-shaped RP-type manganese oxide polycrystalline material rod, moving the seed crystals and the polycrystalline material rods in the same direction and at the same speed to directionally melt the polycrystalline material rods, and crystallizing at the end parts of the seed crystals to obtain Ca with the chemical formulan+ 1MnnO3n+1An RP-type manganese oxide single crystal (n-1). In the process of single crystal growth, the heating power of a laser heating device is 260W, the rotating speed of a material rod is 15r/min, the rotating speed of seed crystals is 20r/min, and the single crystal growth rate is 2mmThe oxygen pressure was 0.87MPa per hour.
The obtained chemical formula is Can+1MnnO3n+1Fig. 4 shows an XRD pattern of the powder of the RP-type manganese oxide single crystal (n ═ 1) and an XRD pattern of the cleavage plane of the RP-type manganese oxide single crystal.
As can be seen from FIG. 6, it is compared with Ca prepared by the infrared float zone melting methodn+1MnnO3n+1Compared with the method (shown as a in figure 6), the method for preparing the high-quality single-phase Ca by adopting the laser float zone melting method has the advantage that (n-1) contains more impure phasesn+1MnnO3n+1(n-1) RP type manganese oxide single crystal (shown in fig. 6, b), and prepared by the laser float zone melting method according to fig. 6, having a chemical formula of Can+1MnnO3n+1The ingot of (n ═ 1) RP type manganese oxide single crystal may have a length of at least 5 cm.
Example 2
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 1), this example was different from example 1 in that: in the third step, the single crystal growth rate was 4 mm per hour, and the oxygen pressure was 0.7 MPa.
Example 3
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 1), this example was different from example 1 in that: in the first step, the temperature of the second calcination and the third calcination is 1350 ℃; in the third step, the heating power of the laser heating device is 276W, the rotating speed of the material rod is 15r/min, the rotating speed of the seed crystal is 30r/min, and the single crystal growth rate is 3.5 mm per hour.
Example 4
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 1), this example was different from example 1 in that:
in the first step, the first block is subjected to a primary calcination at 1000 ℃ for 12 hours, the second block is subjected to a secondary calcination at 1200 ℃ for 8 hours, and the third block is subjected to a tertiary calcination at 1300 ℃ for 10 hours, all at a rate of 180 ℃ per hour.
In the second step, the manganese oxide strip-shaped material rod is calcined for 8 hours at the temperature of 1300 ℃ to prepare strip-shaped RP type manganese oxide polycrystal material rods, the temperature rising rate of the calcination is 180 ℃ per hour, and the temperature reduction rate is 80 ℃ per hour.
In the third step, the heating power of the laser heating device is 200W, the rotating speed of the material rod is 30r/min, the rotating speed of the seed crystal is 25r/min, the single crystal growth rate is 6mm per hour, and the oxygen pressure is 0.6 MPa.
Example 5
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 1), this example was different from example 1 in that:
in the first step, the second block is calcined at 1150 ℃ for 12 hours and the third block is calcined at 1380 ℃ for 9 hours, all at a rate of 220 ℃ per hour.
In the second step, the manganese oxide strip material rod is calcined for 10 hours at the temperature of 1380 ℃ to prepare the strip RP type manganese oxide polycrystal material rod, the temperature rising rate of the calcination is 220 ℃ per hour, and the temperature reduction rate is 120 ℃ per hour.
In the third step, the heating power of the laser heating device was 300W.
Example 6
Chemical formula is Can+1MnnO3n+1The method for preparing an RP-type manganese oxide single crystal of (n ═ 3) includes the steps of:
the first step is as follows: mixing CaCO3And MnO2Is represented by the chemical formula Can+1MnnO3n+1(n-3) in stoichiometric proportions, CaCO3With MnO2The molar ratio of (A) to (B) is 4: 3. For example, weighing CaCO310.676g of raw material and MnO2Raw material 6.955 g.
The weighed raw materials are placed in an agate mortar and ground for 1 hour, so that the raw materials are porphyrized and uniformly mixed.
Pressing the mixed raw materials into a first block, performing primary calcination at 950 ℃ for 10 hours, taking out the first block subjected to primary calcination, crushing, grinding and mixing the first block, then pressing the mixture into a second block, performing secondary calcination at 1150 ℃ for 10 hours, crushing, grinding and mixing the second block subjected to secondary calcination again, then pressing the mixture into a third block, performing tertiary calcination at 1350 ℃ for 10 hours, grinding and mixing the third block subjected to tertiary calcination, and pressing the mixture into manganese oxide strip bars, wherein the heating rates of all the calcination processes are 200 ℃ per hour.
The second step is that: calcining the manganese oxide strip material rod at 1350 ℃ for 10 hours to prepare the strip RP type manganese oxide polycrystalline material rod, wherein the calcining heating rate is 200 ℃ per hour, and the cooling rate is 100 ℃ per hour.
The third step: putting seed crystals and calcined strip-shaped RP-type manganese oxide polycrystalline material rods into a floating zone melting furnace, adopting laser as a heating light source, melting and butting the end parts of the seed crystals and one end of each strip-shaped RP-type manganese oxide polycrystalline material rod, moving the seed crystals and the polycrystalline material rods in the same direction and at the same speed to achieve directional melting of the polycrystalline material rods and crystallization at the seed crystal ends to obtain Can+1MnnO3n+1An RP-type manganese oxide single crystal (n-3). In the process of growing the single crystal, the heating power of the laser heating device is 240W, the rotating speed of the material rod is 25r/min, the rotating speed of the seed crystal is 30r/min, the growing speed of the single crystal is 3 mm per hour, and the oxygen pressure is 0.6 MPa.
The obtained chemical formula is Can+1MnnO3n+1An XRD pattern of the powder of RP type manganese oxide single crystal of (n ═ 3) is shown in fig. 5.
As shown in the graph a of FIG. 7, high-quality single-phase Ca can be prepared by using the laser float zone melting methodn+1MnnO3n+1(n ═ 3) RP type manganese oxide single crystal; and the chemical formula of Ca prepared by the laser float zone melting method is shown in the diagram b in FIG. 7n+1MnnO3n+1The ingot of (n ═ 3) RP type manganese oxide single crystal may have a length of at least 6 cm.
Example 7
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 3), this example was different from example 6 in that: in the first step, the temperature of the second calcination and the third calcination is 1320 ℃; in the third step, the rotating speed of the material rod is 15r/min, the rotating speed of the seed crystal is 25r/min, and the oxygen pressure is 0.8 MPa.
Example 8
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 3), this example was different from example 6 in that: in the third step, the heating power of the laser heating apparatus was 260W, the single crystal growth rate was 5 mm per hour, and the oxygen pressure was 0.8 MPa.
Example 9
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 3), this example was different from example 6 in that:
in the first step, the first block is subjected to a primary calcination at 900 ℃ for 12 hours, the second block is subjected to a secondary calcination at 1100 ℃ for 12 hours, and the third block is subjected to a tertiary calcination at 1300 ℃ for 10 hours, all at a rate of 180 ℃ per hour.
In the second step, the manganese oxide strip-shaped material rod is calcined for 10 hours at the temperature of 1300 ℃ to prepare strip-shaped RP type manganese oxide polycrystal material rods, the temperature rising rate of the calcination is 180 ℃ per hour, and the temperature reduction rate is 80 ℃ per hour.
In the third step, the heating power of the laser heating device is 200W, the rotating speed of the material rod is 30r/min, the rotating speed of the seed crystal is 30r/min, the single crystal growth rate is 2mm per hour, and the oxygen pressure is 0.6 MPa.
Example 10
This example also applies to the preparation of Can+1MnnO3n+1An RP-type manganese oxide single crystal of (n ═ 3), this example was different from example 6 in that:
in the first step, the first block is calcined at 1000 ℃ for 8 hours for the first time, the second block is calcined at 1200 ℃ for 8 hours for the second time, and the third block is calcined at 1380 ℃ for 8 hours for the third time, all at a rate of 220 ℃ per hour.
In the second step, the manganese oxide strip material rod is calcined for 8 hours at the temperature of 1380 ℃ to prepare the strip RP type manganese oxide polycrystal material rod, the temperature rising rate of the calcination is 220 ℃ per hour, and the temperature reduction rate is 120 ℃ per hour.
In the third step, the heating power of the laser heating device is 300W, the rotating speed of the material rod is 15r/min, the rotating speed of the seed crystal is 20r/min, the single crystal growth rate is 6mm per hour, and the oxygen pressure is 0.87 MPa.
In the specific implementation mode of the invention, laser with better focusing property is adopted to locally and rapidly heat the strip-shaped RP-type manganese oxide polycrystalline material rod, and the laser heating has larger temperature gradient and more uniform temperature distribution, thereby reducing the possibility of component supercooling, ensuring the stability of a melting zone and the whole growth process, and further preparing the RP-type manganese oxide single crystal ingot with the size not less than 5 cm.
In all the above examples, unless otherwise specified, the grinding was carried out in an agate mortar; calcination is carried out in a conventional muffle or rotary sintering furnace, for example, a muffle furnace of type FMJ-08/14, FMJ-08/17 or FMJ-08/18, or a rotary sintering furnace of type QSH-RTF; the floating zone melting furnace can adopt a laser floating zone melting furnace with the model of LFZ-2kW, for example.
What has been described above are merely some embodiments of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept thereof, and these changes and modifications can be made without departing from the spirit and scope of the invention.

Claims (8)

  1. A method for preparing Ruddlesden-Popper type manganese oxide single crystal, comprising the steps of:
    step S1: preparing strip Ruddlesden-Popper type manganese oxide polycrystalline material rods;
    step S2: placing seed crystals and the strip Ruddlesden-Popper type manganese oxide polycrystalline material rods in a floating zone melting furnace, and crystallizing at the ends of the seed crystals by using laser as a heating source to obtain Ruddlesden-Popper type manganese oxide single crystals;
    in the process of obtaining the Ruddlesden-Popper type manganese oxide single crystal, the seed crystal and the strip-shaped Ruddlesden-Popper type manganese oxide polycrystalline material rod rotate relative to each other in opposite directions and move relative to the laser heating source at the same direction and speed;
    the growing conditions of the Ruddlesden-Popper type manganese oxide single crystal are set as follows:
    the strip Ruddlesden-Popper type manganese oxide polycrystalline material rod rotates at the rotating speed of 15r/min-30 r/min;
    the seed crystal rotates at the rotating speed of 20r/min-30 r/min;
    the growth speed of Ruddlesden-Popper type manganese oxide single crystal is 2mm/h-6 mm/h;
    the heating power of a laser used for growing the Ruddlesden-Popper type manganese oxide single crystal is 200W-300W;
    the oxygen pressure in the floating zone melting furnace is 0.6MPa-0.87 MPa.
  2. 2. The method for preparing Ruddlesden-Popper-type manganese oxide single crystal as claimed in claim 1, wherein the strip-shaped Ruddlesden-Popper-type manganese oxide polycrystalline rod is prepared by:
    step S11: repeatedly calcining and processing the ground and mixed raw materials to obtain Ruddlesden-Popper type manganese oxide polycrystalline powder;
    step S12: and pressing the Ruddlesden-Popper type manganese oxide polycrystalline powder into a strip-shaped material rod, and calcining to obtain the Ruddlesden-Popper type manganese oxide polycrystalline material rod.
  3. 3. The method of preparing Ruddlesden-Popper-type manganese oxide single crystal as claimed in claim 2, wherein the calcination process of Ruddlesden-Popper-type manganese oxide polycrystalline powder includes the process steps of press-forming, calcining, crushing and grinding mixing in sequence, wherein the calcination process in the calcination process is performed under the temperature condition that the temperature of each calcination is higher than that of the previous calcination, and the calcination temperature of the pressed bar-shaped charge rod in the step S12 is the same as that of the calcination process in the last calcination process.
  4. 4. The method for preparing Ruddlesden-Popper type manganese oxide single crystal as claimed in claim 3, wherein the step of subjecting the ground and mixed raw material to repeated calcination process to obtain Ruddlesden-Popper type manganese oxide polycrystalline powder comprises the steps of:
    step S111: pressing the grinded and mixed manganese oxide raw material powder into a first block, primarily calcining for 8-12 h at 900-1000 ℃, crushing, grinding and mixing, and pressing into a second block;
    step S112: calcining the second block for 8-12 h at 1100-1200 ℃, crushing, grinding, mixing and pressing into a third block;
    step S113: calcining the third block for 8-10 h at 1300-1380 ℃, crushing the calcined third block, and grinding into powder to obtain Ruddlesden-Popper type manganese oxide polycrystalline powder;
    in the step S12, the condition for calcining the bar-shaped material rod is that the bar-shaped material rod is calcined for 8 to 10 hours at 1300 to 1380 ℃.
  5. 5. The method for preparing Ruddlesden-Popper-type manganese oxide single crystal as claimed in claim 4, wherein the temperature rise rate of all calcination processes is 180 ℃/h-220 ℃/h;
    the temperature reduction rate of the calcination process in the step S12 is 80 ℃/h-120 ℃/h.
  6. 6. The method for producing Ruddlesden-Popper type manganese oxide single crystal as claimed in any one of claims 2 to 5, wherein said raw materials in step S11 are calcium carbonate and manganese dioxide in accordance with the chemical composition formula Can+1MnnO3n+1(wherein n is 1 or 3), fully grinding and uniformly mixing to obtain the product。
  7. 7. The method for producing Ruddlesden-Popper type manganese oxide single crystal as claimed in any one of claims 1 to 5, wherein the chemical composition formula of the produced Ruddlesden-Popper type manganese oxide single crystal is An+1MnnO3n+1Wherein, A is calcium ion, n is 1 or 3.
  8. 8. The method for producing Ruddlesden-Popper-type manganese oxide single crystal as claimed in any one of claims 1 to 5, wherein the crystal structure of the Ruddlesden-Popper-type manganese oxide single crystal is a layered perovskite structure having a space group of I41And/acd (n ═ 1) and Pbca (n ═ 3).
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