CN101550597B

CN101550597B - Method for preparing Cr4+:Ca2GeO4 laser crystal

Info

Publication number: CN101550597B
Application number: CN2009100668375A
Authority: CN
Inventors: 曾繁明; 张山丽; 刘景和; 张莹; 秦杰明; 张学建
Original assignee: Changchun University of Science and Technology
Current assignee: Changchun University of Science and Technology
Priority date: 2009-04-17
Filing date: 2009-04-17
Publication date: 2011-07-27
Anticipated expiration: 2029-04-17
Also published as: CN101550597A

Abstract

A method for preparing Cr<4+>:Ca2GeO4 laser crystal belongs to the technical field of tunable laser crystal. The prior art adopts a spontaneous crystallization method and a cosolvent method for preparing Cr<4+>:Ca2GeO4 laser crystal. The Cr<4+> is generated in the growing process of crystal through directly adding the raw material of chromic oxide. The raw materials of germanium dioxide, etc. are directly added into the flux. The main problems of prior art are low growing speed, small crystal size, more defects in the crystal, untotal transformation of Cr<3+> into Cr<4+> and volatilization ofgermanium dioxide. The method of the invention comprises the following steps: 1. weighting the raw materials of chromic oxide, chromium trioxide, calcium carbonate and germanium dioxide according to astoichiometric ratio, weighting the chromic oxide for an excessive amount for 1-2% (wt); 2. mixing the chromic oxide with the chromium trioxide, synthesizing the chromium dioxide with a hydrothermal synthesis method; 3. executing press forming after mixing the chromium dioxide, the calcium carbonate and germanium dioxide; grinding into powder after high-temperature sintering, high-temperature sintering again for obtaining the growing material; and 4. adopting a czochralski method for growing the Cr<4+>:Ca2GeO4 laser crystal with the obtained growing material.

Description

A kind of Cr＜sup for preparing〉4+＜/sup 〉: Ca＜sub〉2＜/sub〉GeO＜sub〉4＜/sub〉method of laser crystals

Technical field

The present invention relates to a kind of tetravalence chromium germanic acid calcium (Cr that mixes ⁴⁺: Ca ₂GeO ₄) feedstock production and the growing method of laser crystals, belong to the tunable laser crystal technical field.

Background technology

The existing tunable laser crystal that is used for tunable laser mainly contains: Cr ³⁺: BeAl ₂O ₄, Ti ³⁺: Al ₂O ₃, Cr ⁴⁺: Mg ₂SiO ₄And Cr ⁴⁺: Ca ₂GeO ₄, its tuning range is respectively 0.710～0.820 μ m, 0.650～1.000 μ m, 1.167～1.345 μ m and 1.300～1.600 μ m.Cr ⁴⁺: Ca ₂GeO ₄The tuning band of laser crystals comprises many important wave bands, and as to the wave band of eye-safe (greater than 1.4 μ m), optical fiber zero chromatic dispersion zero loss wave band etc., this makes Cr ⁴⁺: Ca ₂GeO ₄Laser crystals can be widely used in fields such as medical science, communication.In addition, Cr ⁴⁺: Ca ₂GeO ₄Laser crystals is a kind of Cr of mixing ⁴⁺Ionic forsterite crystal is a kind of congruent melting compound, and fusing point is 1900 ℃, has advantages such as high gain, low-loss, the parasitic center of oscillation of nothing, and centre wavelength is 1.410 μ m.Cr ⁴⁺: Ca ₂GeO ₄The preparation method of laser crystals is spontaneous crystallization method, flux method, Cr ⁴⁺Be by direct adding chromium sesquioxide raw material, in the crystalline process of growth, produce.

Crystal pulling method is that a kind of seed crystal that utilizes lifts out the crystalline growth method from melt, and its advantage is to obtain high quality, large-sized crystal, can reduce lattice defect, shorten the crystal growth cycle.

No matter be spontaneous crystallization method, flux method, or crystal pulling method, employed raw material all is directly to add in the melt, as adopts preceding two kinds of methods growth Cr ⁴⁺: Ca ₂GeO ₄The employed germanium dioxide raw material of laser crystals is exactly directly to join in the melt.

Summary of the invention

Existing Cr ⁴⁺: Ca ₂GeO ₄Thereby the preparation method's of laser crystals the subject matter low growth cycle that is growth velocity is long, crystalline size is little, contains more defective in the crystal, as wrap, crack, foam etc.Because Cr ⁴⁺Be by direct adding chromium sesquioxide raw material, in the crystalline process of growth, produce, therefore, Cr ³⁺Fail to be converted into fully Cr ⁴⁺Have because the germanium dioxide in the raw material has volatility again, introduce in direct adding mode, the volatilization of generation causes the component skewness.These reasons cause optical quality reductions such as laser crystals tunability.The objective of the invention is to overcome existing Cr ⁴⁺: Ca ₂GeO ₄Laser crystals preparation method's deficiency proposes a kind of preparation Cr for this reason ⁴⁺: Ca ₂GeO ₄The method of laser crystals.

The present invention's method may further comprise the steps:

1, take by weighing raw materials used chromium sesquioxide, chromium trioxide, lime carbonate and germanium dioxide according to stoichiometric ratio, wherein excessive 1～2% (wt) of chromium sesquioxide takes by weighing;

2, chromium sesquioxide and chromium trioxide are mixed synthetic chromium dioxide;

3, chromium dioxide, lime carbonate and germanium dioxide are mixed back compression moulding; Pulverize behind the high temperature sintering, high temperature sintering obtains growth material once more;

4, the growth material growth Cr that adopts crystal pulling method, use to be obtained ⁴⁺: Ca ₂GeO ₄Laser crystals.

The technique effect that is brought by the every technical measures of the present invention has, for obtaining Cr ⁴⁺And prepare chromium dioxide in advance, and, chromium sesquioxide is excessive take by weighing and with the chromium trioxide thorough mixing, can improve Cr ³⁺To Cr ⁴⁺Transforming degree and the homogeneity of feed distribution.Germanium dioxide with other raw materials behind twice sintering, the volatilization problem is resolved, and the waste problem that produces because of the volatilization of germanium dioxide is also solved, and has reduced preparation cost, also improve the crystallization degree of growth material and the homogeneity of component, eliminated the Cr in the growth material ³⁺Perhaps make its remaining quantity be reduced to trace, improved the spectrum and the tunable performance of laser crystals.The employing of crystal pulling method makes growth velocity improve, thereby growth cycle shortens, and crystalline size increases, and lattice defect reduces.Prepared Cr ⁴⁺: Ca ₂GeO ₄The laser crystals size reaches

Embodiment

The employed raw material of the present invention's method comprises chromium sesquioxide, chromium trioxide, lime carbonate, germanium dioxide, Calcium Fluoride (Fluorspan) and calcium chloride, and step is as follows:

1, take by weighing each raw material according to stoichiometric ratio with electronic balance, wherein excessive 1～2% (wt) of chromium sesquioxide takes by weighing.

2, with chromium sesquioxide and chromium trioxide with mixer mechanically mixing 12～24 hours, under 380～400 ℃, the condition of 40～45.0MPa, adopt the synthetic chromium dioxide of hydrothermal synthesis method behind the thorough mixing, reaction equation is as follows:

CrO ₃+Cr ₂O ₃→CrO ₂

2CrO ₃→2CrO ₂+O ₂↑。

3, with chromium dioxide, lime carbonate and germanium dioxide mechanically mixing 12～24 hours on mixer, in the material pressing mould of packing into, with hydropress compression moulding under the pressure of 0.8～1.2MPa, the demoulding obtains raw material block; Raw material block is put into retort furnace, and 1100～1350 ℃ of sintering temperatures 6～8 hours, cooling was come out of the stove; By the XRD test shows, once sintered raw material reaction is also incomplete, with more dephasign, grind powdering after 3～4 hours so raw material block is put into mortar, put into retort furnace once more, the identical time of sintering under uniform temp, the cooling acquisition growth material of coming out of the stove, know that according to the XRD test result characteristic peak is consistent with standard diffraction card, know by the photoelectron spectrum test result not contain Cr in the growth material ³⁺

4, with growth material, calcium chloride and Calcium Fluoride (Fluorspan) mechanically mixing 12～24 hours on mixer, wherein Calcium Fluoride (Fluorspan) and calcium chloride mol ratio are 1: 3～4, the two total quality is 40～50% (wt) of sintered material, its role is to reduce the growth material fusing point, thereby in the crystalline process of growth, form the low temperature phase.

5, growth material is packed in the single crystal growing furnace, under nitrogen atmosphere, adopt Czochralski grown Cr ⁴⁺: Ca ₂GeO ₄Laser crystals, growth parameter(s) is pull rate: 1～2mm/h, seed crystal rotating speed: 20～40rpm, reaction equation is as follows:

xCrO ₂+2CaCO ₃+(1-x)GeO ₂＝Ca ₂Cr _xGe _(1-x)O ₄+2CO ₂↑

Wherein the span of x is: 0.03%≤x≤0.3% (wt).

6, crystal growth finishes, and adopts the in-situ annealing method slowly to cool the temperature to room temperature, takes out crystal.Test result shows that lattice defect is less, does not have Cr in the crystal ³⁺, there is not other impurity phase on the sidewall of crucible yet, this shows that the volatility of raw material problem solves.

Claims

1. one kind prepares Cr ⁴⁺: Ca ₂GeO ₄The method of laser crystals is characterized in that, may further comprise the steps:

(1) take by weighing raw materials used chromium sesquioxide, chromium trioxide, lime carbonate and germanium dioxide according to stoichiometric ratio, wherein the excessive 1～2%wt of chromium sesquioxide takes by weighing;

(2) chromium sesquioxide and chromium trioxide are mixed synthetic chromium dioxide;

(3) chromium dioxide, lime carbonate and germanium dioxide are mixed back compression moulding; Pulverize behind 1100～1350 ℃ of sintering temperatures, sintering under uniform temp obtains growth material once more;

(4) the growth material growth Cr that adopts crystal pulling method, use to be obtained ⁴⁺: Ca ₂GeO ₄Laser crystals, that is:

Growth material is packed in the single crystal growing furnace, under nitrogen atmosphere, adopt Czochralski grown Cr ⁴⁺: Ca ₂GeO ₄Laser crystals, growth parameter(s) is pull rate: 1～2mm/h, seed crystal rotating speed: 20～40rpm, reaction equation is as follows:

x?CrO ₂+2CaCO ₃+(1-x)GeO ₂＝Ca ₂Cr _xGe _(1-x)O ₄+2CO ₂↑，

Wherein the span of x is: 0.03%≤x≤0.3%wt.

2. preparation method according to claim 1 is characterized in that, with chromium sesquioxide and chromium trioxide mechanically mixing 12～24 hours, under 380～400 ℃, the condition of 40～45.0MPa, adopts the synthetic chromium dioxide of hydrothermal synthesis method.

3. preparation method according to claim 1 is characterized in that, with chromium dioxide, lime carbonate and germanium dioxide mechanically mixing 12～24 hours, compression moulding under the pressure of 0.8～1.2MPa, the demoulding obtains raw material block; With raw material block 1100～1350 ℃ of sintering temperatures 6～8 hours; Raw material block is ground powdering after 3～4 hours, identical time of sintering under uniform temp once more, the cooling acquisition growth material of coming out of the stove.

4. preparation method according to claim 1 is characterized in that, with growth material, calcium chloride and Calcium Fluoride (Fluorspan) mechanically mixing 12～24 hours, wherein Calcium Fluoride (Fluorspan) and calcium chloride mol ratio were 1: 3～4, and the two total quality is 40～50%wt of sintered material.