CN1257850A - Process for preparing magnetic material of alkali-earth metal and iron and molybdenum oxides by sol-gel method - Google Patents
Process for preparing magnetic material of alkali-earth metal and iron and molybdenum oxides by sol-gel method Download PDFInfo
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- CN1257850A CN1257850A CN 99114586 CN99114586A CN1257850A CN 1257850 A CN1257850 A CN 1257850A CN 99114586 CN99114586 CN 99114586 CN 99114586 A CN99114586 A CN 99114586A CN 1257850 A CN1257850 A CN 1257850A
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Abstract
A magnetic material is prepared from the alkali-earth metal nitrate A(NO3)2, where A is Ca, Sr, or Ba, ammonium molybdate and iron nitrate solution through sequential mixing in acidic condition, liquid-phase reaction to form wel gel, baking, and high-temp post-treating to obtain the megnetic material of alkali-earth metal-iron molybdenum oxide (A2FeMoO6) or the iron molybdenum oxide of multi-element alkali-earth metal (A2-2xA'2xFeMoO6). Its advantages are low sinter temp, high monophase nature and controllable grain size of polycrystal material, and high magnetic resistance effect.
Description
The present invention relates to the preparation method of magnetic material of alkali-earth metal and iron and molybdenum oxides.
Orderly perovskite structure alkali-earth metal and iron and molybdenum oxides A
2FeMoO
6The iron-molybdenum oxide A of (wherein A is alkali earth metal Ca, Sr, Ba etc.) or polyacid base earth metals
2-2xA ＇
2xFeMoO
6(wherein A and A ' are different Ca, Sr, Ba etc., 0＜x＜1) because of it has good ferromagnetic conductive characteristic, just causes people's attention as far back as five sixties.Recently it is found that this compounds has the negative magneto-resistance effect of room temperature low field, promptly adding under the magnetic field condition that the resistivity of material has obvious reduction.This discovery makes this class material might become ideal magnetosensitive sense material and is used for fields such as read-write head, high density magnetic recording, thereby caused the extensive concern of scientific and technological circle.
The existing preparation method of this class material adopts traditional solid reaction process, promptly adopts oxide compound (AO, wherein A=Ca, Sr, Ba etc.), the ferric oxide (Fe of alkaline-earth metal
2O
3) and molybdenum oxide (MoO
3) by certain stoicheiometry weighing, through mixing, grinding and compressing tablet calcining (pre-burning), again through repeatedly grinding, compressing tablet and calcining, at last at evacuated sealed ceramic pipe or under protection of inert gas, high temperature sintering.Prepare strontium iron-molybdenum oxide (Sr at internationally famous periodical Britain " nature " magazine (Nature, 1998 the 395th 15 phases of volume, the 677th page) report with solid reaction process if any Japanese scientist
2FeMoO
6), be at hydrogen (H at last
2) and the gas flow ratio of argon (Ar) be that 1200 ℃ of sintering formed in 2 hours in 1: 100 the mixed gas, this compound polycrystalline bulk at room temperature has certain magneto-resistance effect.
This solid state reaction preparation method repeatedly grinds, calcines and increase the labour intensity except needs, usually need higher sintering temperature, gained polycrystalline material single phase property is relatively poor, grain-size is bigger, experiment shows that the magneto-resistance effect of grain-size and material has direct relation, usually grain-size is more little, and magneto-resistance effect is big more.
The objective of the invention is to overcome solid state reaction preparation method's deficiency, provide a kind of and can realize that low-temperature sintering becomes phase, it is better to obtain single phase property, and grain-size is little, the preparation method of the magnetic material of alkali-earth metal and iron and molybdenum oxides that magneto-resistance effect is big.
The present invention adopts the nitrate A (NO of alkaline-earth metal
3)
2(A=Ca, Sr, Ba etc.), ammonium molybdate, and iron nitrate is pressed the stoicheiometry weighing, be configured to the aqueous solution respectively, under acidic conditions, mix by a graded, generate a kind of wet gel through liquid phase reaction, again wet gel is dried, through repeatedly grind and under differing temps pre-burning obtain the pre-burning powder, with pre-burning powder or its compressing tablet, put into mobile H
2, sintering in the Ar mixed gas, obtain magnetic material of alkali-earth metal and iron and molybdenum oxides powder or bulk.
The advantage of the inventive method is: can reduce sintering temperature, obtain single phase property polycrystalline material preferably; Can control grain-size by different sintering temperatures, thereby reach the purpose of the magneto-resistance effect that improves material; Be suitable for preparation in enormous quantities, reduce labour intensity and energy consumption.
The inventive method can be further specified by following embodiment:
1. step 1: reagent weighing and formulations prepared from solutions.Get alkine earth metal nitrate A (NO
3)
2(as Ca (NO
3)
24H
2O, Sr (NO
3)
2Or Ba (NO
3)
2Deng), Ammonium Molybdate Tetrahydrate ((NH
4)
6Mo
7O
244H
2O) and iron nitrate (Fe (NO
3)
39H
2O) with molecular formula A
2FeMoO
6Press the stoicheiometry weighing, be mixed with the aqueous solution respectively with deionized water.
Step 2: preparing gel.At A (NO
3)
2Slowly splash into concentrated nitric acid (HNO in the solution
3) become acidic solution, splash into HNO
3Amount be that unit is (NH with the mole number
4)
6Mo
7O
244H
24.8～20 times of O mole number; To be with tart alkine earth metal nitrate solution to mix then and stir evenly, at last with Fe (NO with ammonium molybdate solution
3)
3Solution is poured in the above-mentioned mixing solutions and is stirred fast, places that solution becomes the light green wet gel after several minutes.As weighing analytical pure Sr (NO
3)
29.1g (or Ca (NO
3)
24H
2O (content 99%) 10.2g, Ba (NO
3)
211.2g), be configured to the about 50ml of the aqueous solution, with the dense HNO of 1.8ml
3Splash into wherein, again weighing (NH
4)
6Mo
7O
244H
2O (content 99%) 3.8g and Fe (NO
3)
39H
2O (content 98%) 8.8g is made into the 30ml aqueous solution respectively, mixes to obtain wet gel by above-mentioned steps.Processing through following step 3 can obtain final product Sr again
2FeMoO
6About 9g (or Ca
2FeMoO
6About 7g, Ba
2FeMoO
6About 11g).
Step 3: gel oven dry and high-temperature post-treatment.The wet gel that step 2 is obtained is placed in 60～150 ℃ the baking oven and toasts, and up to oven dry, is warming up to 250～300 ℃ of further heating 6 hours again.Last wet gel has become reddish-brown block or powder, to put into 500 ℃ of stove pre-burnings 6 hours after its grinding, ground 700 ℃ of pre-burnings again 6 hours, behind the furnace temperature naturally cooling, obtain the pre-burning powder after fully grinding again, put into sealable vitrified pipe or quartz glass tube with the pre-burning powder or with its tablet forming, feed H in will managing
2With the mixed gas of Ar, under different sintering temperatures and gas flow ratio condition, can obtain the various grain sizes and the final product Ca of purity mutually
2FeMoO
6, Sr
2FeMoO
6Or Ba
2FeMoO
6(powder or bulk).As with Sr
2FeMoO
6Be example, with compressing tablet at H
2With the gas flow ratio of Ar be in 1: 20 the mixed flow gas, 900 ℃ of temperature sintering 3 hours, can obtain grain-size was the single-phase polycrystalline Sr of 20～30nm
2FeMoO
6Bulk, its magneto-resistance effect at room temperature exceed 2～4 times than the product of traditional solid reaction process preparation.Constant as other condition, 1000 ℃ of temperature sintering 3 hours, can obtain the single-phase polycrystalline Sr of the about 60nm of grain-size
2FeMoO
6Bulk, and its magneto-resistance effect obviously reduces.
2. as described in example 1 above, the gel process for preparing of step 2 can adopt following steps to make: with dense HNO
3Splash into Fe (NO
3)
3Make acidic solution in the aqueous solution, splash into HNO
3Amount be that unit is (NH with the mole number
4)
5Mo
7O
244H
27.7～9.7 times of O mole number; Then with acid Fe (NO
3)
3Solution is poured in the ammonium molybdate solution, and the limit bevelling stirs fast, begins to occur throw out, and very fast the disappearance fully or substantially of postprecipitation becomes green transparent solution, the Ca (NO that will configure this moment immediately
3)
2, Sr (NO
3)
2Or Ba (NO
3)
2The aqueous solution is poured into wherein and is stirred, and places that mixing solutions becomes the light green wet gel after several minutes.Other step is all identical with embodiment 1 and make final product A
2FeMoO
6
3. among the embodiment 1 and 2, the used concentrated nitric acid of configuration acidic solution can have ammonium nitrate (NH in the preparation of the wet gel of step 2
4NO
3) the solution replacement, can make wet gel equally.The mixing order of several solns and splash into NH
4NO
3Amount be that unit is (NH with the mole number
4)
6Mo
7O
244H
2Multiple relation and the embodiment 1 and the 2 required HNO of O molar weight
3Unanimity, other step are also identical with embodiment 1 and make final product A
2FeMoO
6
4. for the iron-molybdenum oxide A for preparing the polyacid base earth metals
2-2xA ＇
2xFeMoO
6(wherein A is different Ca, Sr, Ba with A ＇, 0＜x＜1) is as long as press two kinds of alkine earth metal nitrate A of stoicheiometry weighing (NO
3)
2With A ＇ (NO
3)
2Be mixed with the aqueous solution, at first it mixed, other steps such as wet gel preparation and HNO
3Or NH
4NO
3Consumption etc. all identical with embodiment 1,2 and 3, thereby make the iron-molybdenum oxide magneticsubstance of the polyacid base earth metals of different components.
Above embodiment all can press stoicheiometry as required and amplify, and batch preparations goes out the magnetic material of alkali-earth metal and iron and molybdenum oxides that single phase property is good, grain-size is controlled.
Claims (5)
1. Prepared by Sol Gel Method alkali-earth metal and iron and molybdenum oxides A
2FeMoO
6The iron-molybdenum oxide A of magneticsubstance or polyacid base earth metals
2-2xA '
2xFeMoO
6(wherein A and A ＇ are different alkali earth metal Ca, Sr, Ba etc., 0＜x＜1) is characterized in that adopting the nitrate A (NO of alkaline-earth metal
3)
2, ammonium molybdate and iron nitrate Fe (NO
3)
3Press the stoicheiometry weighing, be configured to the aqueous solution respectively, under acidic conditions, mix, generate a kind of wet gel,,,, put into mobile H pre-burning powder or its compressing tablet through repeatedly grinding and pre-burning obtains the pre-burning powder again with the wet gel oven dry through liquid phase reaction by a graded
2, sintering in the Ar mixed gas, obtain alkali-earth metal and iron and molybdenum oxides powder or bulk.
2. the method for claim 1 is characterized in that the preparation of wet gel can be adopted (the NO at alkine earth metal nitrate A
3)
2Slowly splash into concentrated nitric acid HNO in the aqueous solution
3, acid nitrate solution that obtains and Ammonium Molybdate Tetrahydrate (NH
4)
6Mo
7O
244H
2The aqueous solution of O is again with Fe (NO
3)
3Solution is poured into wherein and is stirred, and places and obtains wet gel after several minutes, splashes into HNO
3Amount be that unit is (NH with the mole number
4)
6Mo
7O
244H
24.8～20 times of O mole number, with wet gel 60～150 ℃ of drying in oven, further heated 6 hours at 250～300 ℃ again, after grinding in stove respectively 500 ℃ of pre-burnings and 700 ℃ 6 hours, behind the furnace temperature naturally cooling, fully grind again and obtain the pre-burning powder, put into sealable vitrified pipe or quartz glass tube, feed H in will managing with the pre-burning powder or with its tablet forming
2, Ar mixed gas, under different sintering temperatures and gas flow ratio condition, can obtain the various grain sizes and the magnetic material of alkali-earth metal and iron and molybdenum oxides Ca of purity mutually
2FeMoO
6, Sr
2FeMoO
6Or Ba
2FeMoO
6Powder or bulk.
3. the method for claim 1 is characterized in that the wet gel preparation can adopt (the NO at Fe
3)
3Splash into dense HNO in the aqueous solution
3Make acidic solution, splash into HNO
3Amount be that unit is (NH with the mole number
4)
6Mo
7O
244H
27.7～9.7 times of O mole number are then with acid Fe (NO
3)
3Solution is poured in the Ammonium Molybdate Tetrahydrate solution, and the limit bevelling stirs fast, begins to occur throw out, waits precipitation fully or after basic the disappearance, the nitrate aqueous solution that will configure is poured into wherein and stirred immediately, places and obtains wet gel after several minutes.
4. as claim 1,2 and 3 described methods, it is characterized in that the used concentrated nitric acid of configuration acidic solution can have ammonium nitrate NH in the wet gel preparation
4NO
3Solution replaces, and splashes into NH
4NO
3Amount be that unit is (NH with the mole number
4)
6Mo7O
244H
2The multiple relation of O molar weight is identical with the amount of claim 2 and 3 described nitric acid.
5. the method for claim 1 is characterized in that preparing the iron-molybdenum oxide A of polyacid base earth metals
2-2xA ＇
2xFeMoO
6, be by two kinds of alkine earth metal nitrate A of stoicheiometry weighing (NO
3)
2With A ＇ (NO
3)
2Be mixed with the aqueous solution, at first it mixed, carry out preparing gel and high-temperature post-treatment again and make the iron-molybdenum oxide magneticsubstance of the polyacid base earth metals of respective components.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99114586 CN1257850A (en) | 1999-11-30 | 1999-11-30 | Process for preparing magnetic material of alkali-earth metal and iron and molybdenum oxides by sol-gel method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99114586 CN1257850A (en) | 1999-11-30 | 1999-11-30 | Process for preparing magnetic material of alkali-earth metal and iron and molybdenum oxides by sol-gel method |
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|---|---|
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|---|---|---|---|
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102633495A (en) * | 2012-04-11 | 2012-08-15 | 南京大学 | Preparation method of room-temperature ferromagnetic Sr2FemMonO6 ceramic |
| CN104103822A (en) * | 2013-04-12 | 2014-10-15 | 清华大学 | Preparation method of lithium ion battery cathode material |
| CN104313632A (en) * | 2014-10-24 | 2015-01-28 | 清华大学 | Solid oxide electrolysis cell cathode material as well as preparation method and application thereof |
| CN106669705A (en) * | 2016-12-26 | 2017-05-17 | 阳泉煤业（集团）有限责任公司 | Catalyst used for methanol ammoxidation and preparation and forming method thereof |
| CN107413351A (en) * | 2017-06-14 | 2017-12-01 | 安徽大学 | A kind of willow leaf shape high efficiency photocatalyst Sr2FeMoO6Preparation method |
-
1999
- 1999-11-30 CN CN 99114586 patent/CN1257850A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102633495A (en) * | 2012-04-11 | 2012-08-15 | 南京大学 | Preparation method of room-temperature ferromagnetic Sr2FemMonO6 ceramic |
| CN104103822A (en) * | 2013-04-12 | 2014-10-15 | 清华大学 | Preparation method of lithium ion battery cathode material |
| CN104313632A (en) * | 2014-10-24 | 2015-01-28 | 清华大学 | Solid oxide electrolysis cell cathode material as well as preparation method and application thereof |
| CN106669705A (en) * | 2016-12-26 | 2017-05-17 | 阳泉煤业（集团）有限责任公司 | Catalyst used for methanol ammoxidation and preparation and forming method thereof |
| CN107413351A (en) * | 2017-06-14 | 2017-12-01 | 安徽大学 | A kind of willow leaf shape high efficiency photocatalyst Sr2FeMoO6Preparation method |
| CN107413351B (en) * | 2017-06-14 | 2019-10-25 | 安徽大学 | A kind of willow leaf shape high efficiency photocatalyst Sr2FeMoO6Preparation method |
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