CN110791287B - Rare earth doped tungsten molybdate and preparation method and application thereof - Google Patents

Abstract

The invention discloses a rare earth doped tungsten molybdate with a chemical formula of Sr _1‑x Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 Wherein x is more than or equal to 0.05 and less than or equal to 0.25. The invention also discloses a preparation method of the rare earth doped tungsten molybdate, which comprises the following steps: s1, according to formula Sr _{1‑ x} Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 Respectively weighing samarium salt, strontium salt, tungstate and molybdate according to the stoichiometric ratio; s2, adding samarium salt and strontium salt into water to dissolve, adding tungstate and molybdate to dissolve and mix uniformly, then adjusting the pH to be more than or equal to 9, carrying out hydrothermal reaction, cooling to room temperature, centrifuging to obtain precipitate, washing and drying to obtain the rare earth doped tungsten molybdate. The invention also discloses application of the rare earth doped tungsten molybdate in solid electrolyte. The invention has good conductive performance and sintering compactness, low sintering temperature and good sintered body conductivity, and can be used for solid electrolyte.

Description

Rare earth doped tungsten molybdate, preparation method and application thereof

technical field

The invention relates to the technical field of self-activating light-emitting materials, in particular to a rare earth-doped tungsten molybdate, a preparation method and an application thereof.

Background technique

The tungstomolybdate powder does not need to be doped with some rare earth ions for activation, and can generate very efficient fluorescence under the excitation of some special light, so it can be concluded that doping the matrix with other activated ions can be very obvious. to improve the luminescence properties of the matrix; the tungsten molybdate also has the properties of maintaining good stability and excellent ionic conductivity under high temperature conditions. Tungsten molybdate oxides with an ABO ₄ (A=Ca, Sr, Ba, etc.; B=W, Mo) type scheelite structure are typical oxygen ion conductors. Tungstomolybdate is very suitable as a light-emitting material, and has very important applications in the fields of laser devices, ion conductors of oxides, etc.

At present, the preparation of tungstomolybdic acid powder mainly focuses on the traditional solid-phase reaction method. However, the powder prepared by this method is easy to agglomerate and requires a relatively high sintering temperature (generally 1150-1250° C.) to obtain a relatively dense material. In order to improve the properties of such materials, people are exploring the preparation of such materials by hydrothermal method, sol-gel method and other soft chemical methods, but the tungstomolybdic acid powder prepared by hydrothermal method is often used in the field of luminescent materials, and is rarely used in the field of luminescent materials. electrolyte material.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background technology, the present invention proposes a rare earth doped tungsten molybdate and a preparation method and application thereof. The present invention has good electrical conductivity and sintering compactness; The shape is regular, the size is uniform, the grain distribution is reasonable, and the compacted material can be sintered into a sintered body with a dense structure, and the required sintering temperature is low, which can reduce the sintering energy consumption; and the prepared sintered body has good electrical conductivity. performance, can be used in solid electrolytes.

The chemical formula of a rare earth-doped tungsten molybdate proposed by the present invention is Sr _1-x Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , wherein 0.05≤x≤0.25.

Preferably, x=0.1.

The present invention also proposes a method for preparing the above-mentioned rare earth doped tungsten molybdate, comprising the following steps:

S1, according to the chemical formula Sr _1-x Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium salt, strontium salt, tungstate and molybdate by stoichiometric ratio;

S2. Add samarium salt and strontium salt to water to dissolve, then add tungstate and molybdate to dissolve and mix, then adjust pH ≥ 9, perform hydrothermal reaction, cool to room temperature, centrifuge to collect precipitate, wash, and dry to obtain rare earth doped Hetero tungsten molybdate.

Preferably, pH=9-11.

Preferably, the pH may be 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.

Preferably, pH=9.

Preferably, the temperature of the hydrothermal reaction is 160-200° C., and the time of the hydrothermal reaction is 20-28 h.

Preferably, the temperature of the hydrothermal reaction is 180° C., and the time of the hydrothermal reaction is 24 h.

Preferably, the samarium salt is at least one of samarium nitrate and samarium nitrate hydrate.

Preferably, the strontium salt is at least one of strontium nitrate and strontium nitrate hydrate.

Preferably, the tungstate is at least one of ammonium tungstate and ammonium tungstate hydrate.

Preferably, the molybdate is at least one of ammonium molybdate and ammonium molybdate hydrate.

Preferably, the pH is adjusted with ammonia or nitric acid.

The invention also proposes the application of the above rare earth doped tungsten molybdate in solid electrolyte.

The present invention selects rare earth Sm and Sr doped tungsten molybdate, and selects an appropriate doping amount, so that the present invention has good electrical conductivity and sintering compact performance; selects the hydrothermal method for preparation, and adjusts the appropriate pH, so that the Rare earth doped tungsten molybdate has a pure phase scheelite structure without other heterocrystalline phases; and through suitable pH and hydrothermal reaction conditions, rare earth doped tungsten molybdate has smaller particle size and regular crystal morphology , the size is uniform, the grain distribution is reasonable, and the compacted and compacted material can be sintered into a sintered body with a dense structure, and the required sintering temperature is low, which can reduce the sintering energy consumption; and the prepared sintered body has good electrical conductivity. for solid electrolytes.

Description of drawings

Figure 1 is a TG curve diagram of rare earth doped tungsten molybdate.

Figure 2 is the XRD diffraction pattern of rare earth doped tungsten molybdate obtained at different pH.

Figure 3 is the SME picture of the cross-section of the rare earth doped tungsten molybdate sintered body obtained at different pH.

FIG. 4 is a curve of the conductivity of tungsten molybdate doped with different amounts of Sm as a function of temperature.

Figure 5 is an Arrhenius plot of the ionic conductivity of tungstomolybdate doped with different amounts of Sm.

Detailed ways

Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments.

Example 1

A preparation method of rare earth doped tungsten molybdate, comprising the following steps:

S1, according to the chemical formula Sr _0.95 Sm _0.05 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium salt, strontium salt, tungstate and molybdate by stoichiometric ratio;

S2. Add samarium salt and strontium salt to water to dissolve, then add tungstate and molybdate to dissolve and mix, then adjust pH ≥ 9, perform hydrothermal reaction, cool to room temperature, centrifuge to collect precipitate, wash, and dry to obtain rare earth doped Hetero tungsten molybdate.

Example 2

A preparation method of rare earth doped tungsten molybdate, comprising the following steps:

S1, according to chemical formula Sr _0.75 Sm _0.25 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium nitrate, strontium nitrate, ammonium tungstate and ammonium molybdate by stoichiometric ratio;

S2. Add samarium nitrate and strontium nitrate to water to dissolve, then add ammonium tungstate and ammonium molybdate to dissolve and mix, then adjust pH=11, perform hydrothermal reaction at 160°C for 28h, cool to room temperature, centrifuge at 2500rpm for 3min to get the precipitate, and wash , drying to obtain rare earth doped tungsten molybdate.

Example 3

A preparation method of rare earth doped tungsten molybdate, comprising the following steps:

S1, according to chemical formula Sr _0.8 Sm _0.2 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium nitrate, strontium nitrate, ammonium tungstate and ammonium molybdate by stoichiometric ratio;

S2. Add samarium nitrate and strontium nitrate to the water to dissolve, then add ammonium tungstate and ammonium molybdate to dissolve and mix, then adjust pH=10, hydrothermally react at 200°C for 20h, cool to room temperature, centrifuge at 2500rpm for 3min to get the precipitate, and wash , drying to obtain rare earth doped tungsten molybdate.

Example 4

A preparation method of rare earth doped tungsten molybdate, comprising the following steps:

S1, according to chemical formula Sr _0.9 Sm _0.1 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium nitrate hexahydrate, strontium nitrate, ammonium tungstate hydrate and ammonium molybdate tetrahydrate according to the stoichiometric ratio;

S2. Add samarium nitrate hexahydrate and strontium nitrate to water to dissolve, then add ammonium tungstate hydrate and ammonium molybdate tetrahydrate to dissolve and mix, then adjust pH=9, perform hydrothermal reaction at 180°C for 24h, cool to room temperature, 2500rpm The precipitate was collected by centrifugation for 3 min, washed and dried to obtain rare earth doped tungsten molybdate.

Take the above rare earth doped tungsten molybdate for TG analysis, the results are shown in Figure 1, Figure 1 is the TG curve of the rare earth doped tungsten molybdate, it can be seen from Figure 1 that the mass loss during the heating process of the powder can be roughly divided into three Stage: The first is from room temperature to 200°C, and the loss of the sample is about 0.5%. The main reasons are the evaporation of the crystal water contained in it and the volatilization of a small amount of volatile impurities. When the temperature is programmed from 200°C to 550°C, it can be clearly seen that the TG curve has a rapid decline process, and the loss of the sample is about 2.75%. The main reason may be that with the increase of temperature, the powder contained in the powder Caused by the decomposition of nitrates, etc. When the temperature is higher than 500 °C, the mass of the powder slowly decreases until it remains unchanged, which indicates that each reaction is basically completed and a stable solid solution is formed.

Example 5

pH=7, other is the same as Example 4.

Example 6

pH=11, the others are the same as in Example 4.

XRD analysis was carried out on the rare earth doped tungsten molybdate, SrWO ₄ and SrMoO ₄ of Examples 4-6, and the results are shown in Figure 2. Figure 2 is the XRD diffraction pattern of the rare earth doped tungsten molybdate obtained at different pH. 2 It can be seen that under different pH, there are impurity peaks between crystal plane (101) and crystal plane (112), and the impurity peak gradually decreases with the increase of pH. It is very low, and there is no obvious impurity peak when pH=11; at the same time, the XRD pattern can also clearly reflect that with the increase of pH during the hydrothermal reaction, the peak height is more obvious. It can be shown that in the process of making powder by hydrothermal method, the pH of the reaction sample should be increased as much as possible to reduce the existence of impurity peaks and improve the crystallization performance to obtain better powder, so pH≥9 is selected.

Take Example 4 and Example 6 to prepare sintered bodies respectively. The preparation method of the sintered body is as follows: take rare earth doped tungsten molybdate, add a drop of polyvinyl alcohol ethanol solution and grind until no powder adheres to the mortar wall, take 1.2 g. The ground powder was pressed into tablets, heated to 650°C at a rate of 2°C/min, held for 3 hours, then heated to 845°C at a rate of 1.5°C/min, held for 2 hours to obtain a rare earth doped tungsten molybdate sintered body.

SME scanning was carried out on the cross-sections of the rare earth-doped tungsten molybdate sintered bodies prepared in Example 4 and Example 6. The results are shown in Figure 3. Figure 3 is the SME pictures of the cross-sections of the rare earth-doped tungsten molybdate sintered bodies obtained at different pHs. It can be seen from Figure 3 that 1. The smaller the crystal grains generated by the samples with higher pH during the hydrothermal reaction process, the closer the grain size is to the nanoscale; 2. When the sintering temperature is the same, when pH=9, the cross section of the sintered body There is no obvious pores, indicating that the sintered body has good compactness and meets the requirements of being used as an electrolyte material for solid batteries. When pH=11, the SEM of the cross-section of the sintered body shows that there are many pores in the sample. This shows that the higher the pH during the hydrothermal reaction, the smaller the grain size, and the higher the temperature required for the sintering process.

Example 7

The chemical formula of the rare earth-doped tungsten molybdate is Sr _0.95 Sm _0.05 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , and the preparation method thereof is the same as that in Example 4.

Example 8

The chemical formula of the rare earth doped tungsten molybdate is Sr _0.85 Sm _0.15 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , and the preparation method thereof is the same as that in Example 4.

Example 9

The chemical formula of the rare earth doped tungsten molybdate is Sr _0.8 Sm _0.2 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , and the preparation method thereof is the same as that in Example 4.

Example 10

The chemical formula of the rare earth doped tungsten molybdate is Sr _0.75 Sm _0.25 (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , and the preparation method thereof is the same as that in Example 4.

Take Example 4 and Examples 7-10 to prepare sintered bodies respectively. The preparation method of the sintered bodies is as follows: take rare earth doped tungsten molybdate, add a drop of polyvinyl alcohol ethanol solution and grind until no powder adheres to the mortar wall, Take 1.2 g of the ground powder into tablets, heat it up to 650 °C at a rate of 2 °C/min, hold it for 3 hours, then heat it up to 845 °C at a speed of 1.5 °C/min, and keep it for 2 hours to obtain rare earth doped tungsten molybdate sintering body.

The Arrhenius curves of the electrical conductivity and ionic conductivity of the sintered bodies obtained in Example 4 and Example 7-10 were tested. The results are shown in Figure 4 and Figure 5. Figure 4 is the electrical conductivity of tungsten molybdate doped with different amounts of Sm. Figure 5 shows the Arrhenius curve of ionic conductivity of tungsten molybdate doped with different amounts of Sm;

It can be seen from Figure 4 that with the increase of Sm content, the electrical conductivity gradually increases, because with the increase of Sm content, Sm ³⁺ replaces Sr ²⁺ , in order to maintain electrical neutrality, oxygen will be discharged from the lattice. , forming oxygen vacancies, which greatly improves its ionic conductivity, so that the ionic conductivity increases. When the Sm content exceeds 0.1, the conductivity will decrease, because too many oxygen vacancies will occur. The oxygen vacancies and solid solution The association of cations will reduce the electrical conductivity; when the Sm content is 0.1, the rare earth doped tungsten molybdate reaches the highest electrical conductivity at 800 ℃, and the highest electrical conductivity is 5.9×10 ^-2 S·cm ^-1 ;

It can be seen from Figure 5 that the change of the conductivity activation energy has the same law as the conductivity change. When the Sm content exceeds 0.1, the conductivity activation energy will increase; when the Sm content is 0.1, the activation energy is the lowest.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (6)

1. A preparation method of rare earth doped tungstomolybdate, wherein the chemical formula of the rare earth doped tungsten molybdate is Sr _1-x Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , wherein, x=0.1; The preparation method specifically comprises the following steps: S1, according to the chemical formula Sr _1-x Sm _x (MoO ₄ ) _0.5 (WO ₄ ) _0.5 , respectively weigh samarium salt, strontium salt, tungstate and molybdate according to the stoichiometric ratio; S2. Add samarium salt and strontium salt to the water to dissolve, then add tungstate and molybdate to dissolve and mix, then adjust pH=9-11, perform hydrothermal reaction at 160-200℃, and the reaction time is 20- 28h, cooled to room temperature, centrifuged to collect the precipitate, washed, and dried to obtain rare earth-doped tungsten molybdate. 2 . The preparation method of rare earth doped tungsten molybdate according to claim 1 , wherein the temperature of the hydrothermal reaction is 180° C., and the time of the hydrothermal reaction is 24 h. 3 . 3. The preparation method of rare earth-doped tungsten molybdate according to claim 1, wherein the samarium salt is at least one of samarium nitrate and samarium nitrate hydrate; the strontium salt is strontium nitrate and strontium nitrate hydrate at least one of. 4. The preparation method of rare earth-doped tungstomolybdate according to claim 1, wherein the tungstate is at least one of ammonium tungstate and ammonium tungstate hydrate; the molybdate is ammonium molybdate, At least one of ammonium molybdate hydrate. 5. The preparation method of the rare earth-doped tungsten molybdate according to claim 1, wherein the pH is adjusted with ammonia water or nitric acid. 6. The application of the rare earth doped tungstomolybdate prepared by the method for preparing the rare earth doped tungsten molybdate according to claim 1-5 in a solid electrolyte.

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