CN100532320C - Lithium-sodium-cobalt-oxygen thermoelectric ceramic and preparation method thereof - Google Patents

Abstract

The invention relates to a Ni-Na-CoO thermoelectric ceramic material and manufacturing method thereof. A general molecular formula of the cobaltite oxide thermoelectric ceramic material is described as LixNayCoO2, wherein, the lithium and natrium content are 0.375 is less than or equal to x is less than or equal to 0.48 and 0.3 is less than or equal to y is less than or equal to 0.45 respectively; Raw materials are fully mixed at a mole rate of 3x:3y:2 for Li2CO3: Na2CO3:Co3O4 prior to grinding; then the mixture can be punched under 80-120MPa pressure conditions to obtain tablets, in which 0.375 is less than or equal to x is less than or equal to 0.48 and 0.3 is less than or equal to y is less than or equal to 0.45 are maintained; then tablets are sintered in a tubular furnace with recycling oxygen for 24-48 hours under 1103-1173K temperature conditions, and finally the sintered tablets go through a fast cooling to get single-phase polycrystalline bulk crystals. According to the invention, the Ni-Na-CoO based product can serve as a novel thermoelectric material. The product can be obtained through changes of initial ingredients, sintering atmosphere, sintering temperature, sintering time and fast cooling. The material has a large Seebeck coefficient (170-210 Mu V/K) under ambient temperature and a better quality factor compared with the like cobaltite thermoelectric ceramics, thereby allowing a market potential.

Description

Lithium-sodium-cobalt-oxygen thermoelectricity ceramic and preparation method thereof

Technical field

The present invention relates to a kind of lithium-sodium-cobalt-oxygen thermoelectricity ceramic and preparation method thereof.

Background technology

Thermoelectric material has significant Seebeck effect and Peltier effect, thereby can realize the direct conversion between heat energy and the electric energy.The Seebeck effect is a kind of thermoelectric effect, and it is meant will produce certain electromotive force when there is certain temperature difference in the two ends of material.The Peltier effect is the adverse affects of Seebeck effect: when passing to the electric current of certain orientation in the material, can produce heat absorption, exothermic phenomenon respectively at the two ends of material; Change the sense of current, heat absorption, release end of heat are also reverse thereupon.Utilize this Seebeck effect, thermoelectric material is not only the topmost power supply in current degree of depth deep space probing field, but also can be used for the recycling of vehicle exhaust and industrial exhaust heat, sun power, sea energy and underground heat thermo-electric generation have broad application prospects in energy-conservation and environmental protection field.Its Peltier effect then can be applicable to the cooling of electron device (infrared and far-infrared photoconductor, high-speed chip etc.) and aerospacecraft and submarine with many key areas such as conditioning units.

Tradition thermoelectric semiconductor material (as PbTe) is though have higher quality factor (thermoelectric figure of merit), and unstable and be easy to shortcomings such as oxidized when their toxicity, high temperature limits its range of application.The stratiform cobaltates do not have above-mentioned defective, are the novel thermoelectric functional materialss of a class that receives much attention in recent years.But on the index of using, the Seebeck coefficient of the present stratiform cobaltates of developing and quality factor await further to improve.

Summary of the invention

The purpose of this invention is to provide a kind of alternative cobalt oxidation compound pottery and preparation method thereof with heat-flash electrical effect very.The lithium-sodium-cobalt-oxygen compound has Li _xCoO ₂And Na _yCoO ₂Symbiotic structure, this natural superstructure might strengthen the thermoelectricity capability of system.

The general formula of the thermoelectric porcelain of lithium-sodium-cobalt-oxygen is Li _xNa _yCoO ₂, lithium, sodium content are respectively 0.375≤x≤0.48,0.3≤y≤0.45 in the formula.

The preparation method of the thermoelectric porcelain of lithium-sodium-cobalt-oxygen comprises the steps:

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 3x:3y:2, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 80～120MPa, and wherein, lithium, sodium content are respectively 0.375≤x≤0.48,0.3≤y≤0.45;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1103～1173K, and calcination time is 24～48 hours, is quickly cooled to room temperature then and gets final product.

The invention solves the technology of preparing difficult problem of lithium-sodium-cobalt-oxygen pottery.We adopt the technology that is rapidly heated, the volatilization of Lithium Oxide 98min and sodium oxide when having remedied high temperature solid state reaction to a great extent; Sintering has satisfied the thermodynamic condition that forms the lithium-sodium-cobalt-oxygen pottery under flow oxygen and 1103～1173K high temperature, has suppressed the decomposition of sample in the slow temperature-fall period simultaneously by rapid cooling method, thereby has finished the present invention.

Lithium-sodium-cobalt-oxygen can be used as the new thermoelectric material on many Application Areass such as a kind of refrigeration, thermo-electric generation, and has solved the preparation problem of this material.This invention can access the lithium-sodium-cobalt-oxygen bulk sample of high single phase property, for solid basis has been established in its further practical application.

Description of drawings

Fig. 1 is Li _0.48Na _0.45CoO ₂The X-ray diffraction figure of powder;

Fig. 2 is Li _0.48Na _0.45CoO ₂Seebeck coefficient of block (Seebeck coefficient) and the temperature variant curve of quality factor ZT;

Fig. 3 is Li _xNa _yCoO ₂The X-ray diffraction figure of (0.375≤x≤0.48,0.3≤y≤0.45).

Embodiment

That the present invention relates to is single-phase cobaltates thermoelectric ceramic material Li _xNa _yCoO ₂The proportioning raw materials and the synthetic method of (0.375≤x≤0.48,0.3≤y≤0.45), detailed process is as follows:

Embodiment 1

1) purity is higher than 99% Quilonum Retard (Li ₂CO ₃): yellow soda ash (Na ₂CO ₃): tricobalt tetroxide (Co ₃O ₄)=0.72:0.675:1 mol ratio proportioning raw materials weighing uniform mixing, grinding are carried out punching press then and are made compressing tablet under the pressure of 100MPa;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1173K, and calcination time is 30 hours, is cooled fast to room temperature then and can obtains Li _0.48Na _0.45CoO ₂Block.

Can learn that from Fig. 1 the lithium-sodium-cobalt-oxygen that obtains with above process has good single phase property, all X-ray diffraction peaks can both carry out good index, and the unit cell parameters of sample sees Table 1; From Fig. 2, can learn, institute's synthetic lithium-sodium-cobalt-oxygen pottery has thermoelectric property preferably: near room temperature, the Seebeck coefficient of lithium-sodium-cobalt-oxygen pottery (Seebeck coefficient) has reached 182 μ V/K, in addition, the thermoelectric quality factor ZT of its room temperature reaches 0.03, this is also higher in cobaltates, and this explanation lithium-sodium-cobalt-oxygen has bigger application potential as a kind of new thermoelectric material.

Embodiment 2

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 0.675:0.525:1, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 80MPa;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1173K, and calcination time is 24 hours, is quickly cooled to room temperature then and can obtains Li _0.45Na _0.35CoO ₂Block.

Embodiment 3

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 0.6375:0.4875:1, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 100MPa;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1153K, and calcination time is 36 hours, is quickly cooled to room temperature then and gets final product Li _0.425Na _0.3255CoO ₂Block.

Embodiment 4

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 0.6:0.45:1, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 120MPa;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1123K, and calcination time is 40 hours, is quickly cooled to room temperature then and gets final product Li _0.4Na _0.3CoO ₂Block.

Embodiment 5

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 0.5625:0.45:1, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 120MPa;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1103K, and calcination time is 48 hours, is quickly cooled to room temperature then and gets final product Li _0.375Na _0.3CoO ₂Block.

Can learn that from Fig. 3 the lithium-sodium-cobalt-oxygen that obtains with above process all has good single phase property, the unit cell parameters of each sample sees Table 1, and (table 1 is Li _xNa _yCoO ₂Proportioning raw materials, sintering temperature, room temperature Seebeck coefficient and the unit cell parameters of (0.375≤x≤0.48,0.3≤y≤0.45) single-phase sample).In addition, institute's synthetic lithium-sodium-cobalt-oxygen pottery Seebeck coefficient of all having very big room temperature.Under the 300K, the thermoelectric force of 2-5 sample is respectively 212 μ V/K, 179 μ V/K, 188 μ V/K and 175 μ V/K, this is maximum in reporting up to now in cobaltates single_phase system (nothing is separated), illustrates that lithium-sodium-cobalt-oxygen has the advantage of its application as a kind of new thermoelectric material.

Table 1

Claims (2)

1, the thermoelectric porcelain of a kind of lithium-sodium-cobalt-oxygen is characterized in that its general formula is Li _xNa _yCoO ₂, lithium, sodium content are respectively 0.375≤x≤0.48,0.3≤y≤0.45 in the formula.

2, the preparation method of the thermoelectric porcelain of a kind of lithium-sodium-cobalt-oxygen according to claim 1 is characterized in that comprising the steps:

1) with Li ₂CO ₃: Na ₂CO ₃: Co ₃O ₄Mol ratio is the raw material thorough mixing of 3x:3y:2, grinds, and carries out punching press then and obtain compressing tablet under the pressure of 80～120MPa, and wherein, lithium, sodium content are respectively 0.375≤x≤0.48,0.3≤y≤0.45;

2) above-mentioned compressing tablet is placed in the tube furnace of the oxygen that flows, is rapidly heated to calcining temperature, calcining temperature is 1103～1173K, and calcination time is 24～48 hours, is quickly cooled to room temperature then and gets final product.

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