CN1053635C - Water-heating preparation method for fluoride and composite fluoride material under mild condition - Google Patents

Abstract

The hydrothermal preparation method of fluoride and composite fluoride material under mild conditions belongs to the field of inorganic chemistry. The method uses oxides, hydroxides, fluorides, ammonium bifluoride, and water as raw materials, puts them in a reaction kettle according to an appropriate proportion, crystallizes at 80°C-240°C for 1-168 hours, washes, and filters , dried to obtain fluoride or compound fluoride. The invention has simple technological process and equipment, low reaction temperature, easy control of conditions, no poisonous gas, wide source of raw materials, energy saving, and is suitable for industrial production. It is also possible to prepare complex fluoride luminescent materials doped with rare earth ions. The product is pure in phase, low in oxygen content, free of impurities and water of crystallization.

Description

Hydrothermal preparation method of fluoride and composite fluoride materials under mild conditions

The invention belongs to the field of inorganic chemistry, and particularly relates to a hydrothermal preparation method of fluoride, composite fluoride and rare earth ion-doped composite fluoride luminescent material under mild conditions.

Fluorides and composite fluorides are a class of inorganic materials with good optical, electrical and magnetic properties, and composite fluorides doped with rare earth ions are materials with good luminescent properties.

The method for preparing fluoride and compound fluoride close to the present invention is a high-temperature solid-state reaction method. The preparation of composite fluorides by this method must use fluorides as raw materials. The preparation process is to put the solid-phase fluorides into a gold boat and place them under the protection of inert gas after fully grinding, and react at a high temperature of 700°C. The resulting product also undergoes multiple defluorination treatments.

This high-temperature solid-phase reaction method has the following disadvantages: the first, the reactant is a solid-phase fluoride, the raw material has more than two reaction processes, the hydrogen fluoride and other gases that are introduced need to be dried, and the reaction must be carried out in a protective cover, etc. The whole preparation process is complicated; second, the reaction must be carried out under high temperature conditions, and good fluorine pollution prevention measures are required for the whole reaction system, resulting in complicated equipment and large energy consumption; third, due to the existence of harmful gases, not only damage to the equipment Severe corrosion, and will cause poisoning to operators, poor production environment, unsafe; Fourth, the generated fluoride has high oxygen content and many impurities.

In order to overcome the shortcomings of the prior art, the present invention adopts a hydrothermal synthesis method under mild conditions to achieve the purposes of simple process and equipment, safe production, energy saving, pure product phase and low oxygen content.

The hydrothermal preparation method of fluoride and composite fluoride materials under mild conditions uses oxides, hydroxides, ammonium bifluoride and water as raw materials, and puts them in a reaction kettle according to a suitable proportion. The pH value of the reaction mixture is Less than 7, the reaction temperature is 80°C to 240°C, the reaction time is 1-168 hours, and the product can be post-treated to obtain a series of stable fluorides and complex fluorides.

The reaction kettle used can be a closed stainless steel reaction kettle with polytetrafluoroethylene as a liner, and the post-treatment of the product includes filtering, washing and drying at room temperature to obtain a pure solid product.

The oxides in the raw materials mainly include alkali metal oxides or/and alkaline earth metal oxides or/and rare earth oxides.

The present invention is a mild hydrothermal synthesis method for fluorides and composite fluorides, and the material ratio of each compound is shown in Table 1. The reaction temperature is 120°C to 240°C, and the reaction time is 1 hour to 5 days. The resultant was cooled, filtered, washed, and dried at room temperature. The present invention is characterized in that the hydrothermal reaction temperature is much lower than the solid phase reaction temperature, and the D value of the X-ray powder diffraction spectrum of the synthesized product is the same as that of the product synthesized in the prior art.

Table 1. Molar ratio range of various materials Compound Molar ratio of starting material pH value KMgF ₃ KOH:Mg(OH) ₂ :NH ₄ HF ₂ :H ₂ O=1:1:2:100 4-6KMgF ₃ KF: MgF ₂ : H ₂ O=1:1:100 3-7LiBaF ₃ LiOH:Ba(OH) _{2 :} NH ₄ HF 2 : _{H 2} O=2:1:2:200 2-12LiYF ₄ LiOH: _{Y 2} O ₃ :NH ₄ HF ₂ :H ₂ O=2:1:4:500 4KYF ₄ KOH:Y ₂ O ₃ : _{NH 4} HF ₂ :H ₂ O=3:1:3:300 4BaBeF ₄ Ba(OH) ₂ : BeF ₂ :NH ₄ HF ₂ :H ₂ O=1:1:2:200 <7BaY ₂ F ₈ Ba(OH) ₂ :Y ₂ O ₃ :NH ₄ HF ₂ :H ₂ O=2:1:20: 400 <4EuF ₃ Eu ₂ O ₃ :NH ₄ HF 2 : _{H 2} O=1:4:200 <7NdF ₃ Nd ₂ O ₃ :NH 4 HF ₂ : _{H 2 O} =1:4:200 <7LaF ₃ La ₂ O ₃ :NH ₄ HF ₂ :H ₂ O=1:4:200 <7 It can be seen from Table 1 that the raw materials also include fluoride, such as MgF ₂ , KF, etc., which can be a system of fluoride and fluoride. It can also be a system of fluoride, hydroxide, and NH ₄ HF ₂ . From Table 1, the ratio of raw materials for preparing different fluorides or composite fluorides is different, but it can be concluded that the total molar ratio range is alkali metal or/and alkaline earth metal hydroxide: rare earth oxide: NH ₄ HF ₂ : H ₂ O=(2~6):(0~1.5):4:(80~500).

In order to prepare the complex fluoride luminescent material doped with rare earth ions, the raw materials also include oxides or salts of rare earth elements Re=Eu, Sm, Tb, Ce and the like. In the preparation process, the raw materials for synthesizing composite fluorides are placed in a reaction kettle, and rare earth oxides or salts are added in a certain molar ratio, or all the required raw materials are added at the same time, stirred evenly, and crystallized under mild conditions; the obtained The product is preferably subjected to ultrasonic vibration, washed with HCl solution, washed with deionized water until neutral, and dried at room temperature, so as to realize the doping of rare earth ions in the composite fluoride.

The rare earth oxides or salts include, for example, Eu ₂ O ₃ , Sm ₂ O ₃ , Tb(NO ₃ ) ₃ , Ce(NO ₃ ) ₃ and so on.

The present invention uses different reaction conditions from the prior art to synthesize a series of fluoride and compound fluoride crystals. Table 2 shows the crystallographic data of a series of fluoride and composite fluoride crystals synthesized by the preparation method of the present invention using a Rigaku D/MAX-IIIA X-ray diffractometer.

Table 2 Crystallographic data of fluorides and complex fluorides Compounds Unit cell parameters () Crystal structures

a b cKMgF ₃ 3.9522 Cubic LiBaF ₃ 3.9969 Cubic LiYF ₄ 5.116 10.744 Tetragonal KYF ₄ 8.132 10.043 Hexagonal BaBeF ₄ 8.828 5.324 7.043 Orthogonal EuF ₃ 6.610 7.013 4.399 ₃ Orthogonal 7NdF3

The above crystallographic data were corrected with KCL as the internal standard.

The product obtained by the hydrothermal preparation method of the present invention has the same D value of the X-ray powder diffraction spectrum as the product synthesized in the prior art, and also has thermal stability, and can exist stably at high temperatures above 900°C.

The method of the invention also has many advantages. The temperature of the reaction is low, the source of raw materials is wide, there is no two preparation processes, no oxygen and fluorine pollution prevention measures are necessary, and there is no harmful gas in the production environment, so the process is simple, easy to control, simple and non-corrosive equipment, safe production and energy saving . The obtained product is pure in phase, uniform in grain size, free of crystal water, and free of original impurities; only a single product is produced. XPS results show that neither O-F bonds nor O-M-F bonds are formed in the product, indicating that the oxygen content in the product is very high. Low; the synthesized rare earth composite fluoride luminescent body does not change the price of rare earth ions in the alkaline system, which provides a material with practical application significance for the realization of single-matrix three-primary-color luminescent materials. The above advantages are all beneficial to industrial production.

In order to better illustrate the reaction conditions of the present invention, the following examples are listed.

Example 1

Reaction material: KF: 2.9 grams

_MgF2 : 3.1 g

Reaction temperature: 120°C

Response time: 1 hour - 48 hours

Reaction product: KMgF ₃

Example 2

Reaction raw material: LiOH: 2.1 grams

Ba(OH) ₂ : 7.9 g

NH ₄ HF ₂ : 2.8 g

Reaction temperature: 120°C

Response time: 2 days

Reaction product: LiBaF _3Example 3

Reaction raw material: LiOH: 2.1 grams

Ba(OH) ₂ : 7.9 g

NH ₄ HF ₂ : 2.8 g

Reaction temperature: 25°C

Response time: 2 days

The reaction product: LiBaF ₃ +BaF ₂ shows that the reaction temperature has an important influence on the product. Embodiment 4 reaction raw material: Ba(OH) ₂ : 7.9 grams

_BeF2 : 2.4 g

NH ₄ HF ₂ : 2.8 grams Reaction temperature: 140°C Reaction time: 4 days Reaction product: BaBeF ₄ Example 5 Reaction raw material: LiOH: 8.0 grams

Y ₂ O ₃ : 23.0 g

NH ₄ HF ₂ : 57.0 g Reaction temperature: 140°C Reaction time: 5 days Reaction product: LiYF ₄ Example 6 Reaction raw material: KF: 2.9 g

Y ₂ O ₃ : 3.8 g

NH ₄ HF ₂ : 3.8 grams Reaction temperature: 180°C Reaction time: 5 days Reaction product: KYF ₄ Example 7 Reaction raw materials:

Eu ₂ O ₃ : 8.7 g

NH ₄ HF ₂ : 5.6 g Reaction temperature: 240°C Reaction time: 7 days Reaction product: EuF ₃ Example 8

Reaction raw material ratio:

LiOH: _{Y 2} O ₃ :NH ₄ HF ₂ :Eu ₂ O ₃ :H ₂ O=2:1:4:0.01:50C

Reaction temperature: 240°C

Response time: 7 days

Reaction product: LiYF ₄ : Eu ³⁺ Example 9

Reaction raw material ratio:

LiOH:Y ₂ O ₃ :NH ₄ HF ₂ :H ₂ O=2:1:2:500

Reaction temperature: 240°C

Response time: 7 days

Reaction product: miscellaneous crystal Example 10

Reaction raw material ratio:

LiOH:Y ₂ O ₃ :NH ₄ HF ₂ :H ₂ O=1:1:4:500

Reaction temperature: 240°C

Response time: 7 days

Reaction product: miscellaneous crystal Example 11

Reaction raw material ratio:

LiOH: _{Y 2} O ₃ :NH ₄ HF ₂ :H ₂ O=2:1:8:500

Reaction temperature: 240°C

Response time: 7 days

Reaction product: LiYF ₄

By comparing Examples 9 and 10 with Example 11, it can be seen that the ratio of raw materials has a great influence on the generated product.

Claims (3)

1. the hydrothermal preparing process of the complex fluoride material of rare earth fluorine or basic metal, alkaline-earth metal, rare earth element, raw material includes basic metal or/and the oxyhydroxide of alkaline-earth metal, rare earth oxide, ammonium acid fluoride, water; The raw material order is (2～6) in molar ratio: (0～1.5): 4: the proportioning of (80～500) places reactor, the pH value of reaction mixture is less than 7, crystallization is 1～168 hour under 80～240 ℃ of temperature, and resultant is at room temperature dry after cooling, filtration, washing.

2. according to the hydrothermal preparing process of the complex fluoride material of the described rare earth fluorine of claim 1 or basic metal, alkaline-earth metal, rare earth element, it is characterized in that said resultant comprises rare earth ion doped complex fluoride, has the oxide compound of Y, Eu, Nd, La in raw material; Products therefrom is through sonic oscillation, and order is washed till neutrality with HCl solution and deionized water again, and is at room temperature dry.

3. according to the hydrothermal preparing process of the described complex fluoride material of claim 1, it is characterized in that said complex fluoride is KMgF ₃, it is with KF, MgF ₂With water be raw material 1: 1: 100 in molar ratio preparation.