CN105669182A - Method for studying optimum sintering process of gallium-doped zinc oxide ceramic by spark plasma sintering - Google Patents

Abstract

The invention provides a method for studying an optimum sintering process of a gallium-doped zinc oxide (ZnO) ceramic by spark plasma sintering. The method comprises the steps: weighing a ZnO powder and a Ga2O3 powder according to the ratio of Ga[0.00075]Zn[0.99925]O, carrying out ball milling, drying, and sieving, to obtain an evenly-mixed ZnO and Ga2O3 powder; loading the powder into a graphite mold, compacting, placing the graphite mold in a furnace cavity of a spark plasma sintering furnace, and vacuumizing, wherein the pre-pressure is 15 MPa; and increasing room temperature to 600 DEG C within 4 min, followed by heating up at the speed of 10 DEG C/min, when a displacement curve has a maximum peak value, increasing the pressure to 60 MPa, then heating up to 1100 DEG C at the heating-up speed of 10 DEG C/min, carrying out heat preservation for 9 min, when cooling is ended, dropping the pressure to the minimum, and sintering the sample into the ceramic at a time. The process greatly improves the preparation efficiency, and also has the characteristics of one-time sintering to form the ceramic and low energy consumption, is convenient for industrial production, greatly reduces the electrical resistivity of the GZO ceramic, and improves the electrical properties of the ceramic.

Description

The method of a kind of discharge plasma sintering research Ga-doped zinc oxide pottery optimum sintering process

Technical field

The invention belongs to Ga_xZn_1-xThe preparation field of O (abbreviation GZO) conductivity ceramics.

Background technology

ZnO, as II-VI group n type direct broad stopband oxide semiconductor, is a kind of multifunctional material, has many advantages, therefore, cause the attention of a lot of people. First, under normal temperature, the energy gap of ZnO is 3.37eV, and exciton bind energy is 60meV, is approximately 2.4 times of the hot ionization energy of room temperature, higher than other several semiconductor material with wide forbidden band; Secondly, high-quality ZnO monocrystalline can be prepared by simple technology, and the content of Zn element is more in the earth's crust, and therefore the price of ZnO device is also lower; Finally, ZnO is nontoxic to environment, is a kind of environment-friendly materials, and fusing point is very high, has very strong thermostability and chemical stability. So being material by primary study and exploitation in recent years. Ga-doped zinc oxide improves the performance of ZnO, particularly photoelectric properties especially, thus makes it be widely used in scintillator, optoelectronic device, thermoelectric material and sputtering target material etc. The GZO transparent conductive film prepared with Ga-doped zinc oxide sputtering target material is especially owing to the photoelectric properties of its excellence are widely used in the fields such as solar cell, piezoelectric device, liquid-crystal display. Due to the factor of the such as GZO ceramic mass such as arrangement and size of purity, compactness, resistivity and crystal grain thereof, will directly affect the quality of its performance, so high-quality GZO pottery can be prepared have significance. The domestic technology in this field is immature at present, external developed country knows core technology, needed for industrial production, GZO pottery relies on import substantially, and therefore, our currently urgent task determines that the optimum sintering process of GZO pottery is to serve scientific research and suitability for industrialized production. In the last few years about GZO class article report mainly concentrate on thin-film material and powder body material, article report in ceramic-like and performance research thereof is less, and GZO pottery is mainly prepared by traditional high temperature solid-phase sintering method, sintering temperature is higher, time is also very long, waste the energy, it is unfavorable for suitability for industrialized production. At present, only tradition solid-phase sintering method prepares the relevant report of GZO pottery, does not also prepare the relevant report of GZO pottery by discharge plasma sintering (SparkPlasmaSintering is called for short SPS) method.

Discharge plasma sintering is the development nineties and ripe a kind of sintering technology, and it utilizes on and off DC pulse current to be directly energized pressure sintering. Adding a controllable pulse electric current to pressure-bearing conductive die, pulsed current is by also passing through sample itself while mould, and some runs through the gap of sample and mould. Activate crystal grain surface by the part electric current of sample and gap, puncture residual gas in hole, shelf depreciation, even produce plasma body, promote that the local between crystal grain combines, provide an inherent heating source to sample; By the current flow heats mould of mould part, provide an external heating source to sample. In discharge plasma sintering process, sample is simultaneously by inside and outside heating, so, it has very fast heat-up rate. Because discharge plasma sintering has the feature of heat-up rate fast (the fastest 200 DEG C/min), sintering time short (several minutes), sample even compact, so it has been used to sinter various material.

At present, some articles about the optimum sintering process of GZO ceramic tradition solid-phase sintering method are reported successively both at home and abroad, as the people such as M.S.Jang have delivered the article being entitled as " AstudyontheRamanspectraofAl-dopedandGa-dopedZnOceramics " (" research of aluminium plus gallium doping zinc-oxide pottery Raman spectrum ") for 2009 at CurrentAppliedPhysics (modern Application physics journal) on the 9th volume, report and utilize high-temperature solid phase reaction method to prepare the Ga-doped zinc oxide pottery of 6 kinds of different componentss and the research on correlated performance impact thereof, the people such as Wu Muying have delivered, at Journal of Henan University (natural science edition), the article that a section is entitled as " transparent conductivity of Ga-doped zinc oxide film is affected by preparation condition " for 2012 on the 42nd volume, report the Ga-doped zinc oxide conductivity ceramics utilizing high-temperature solid phase reaction method to prepare 6 kinds of different componentss, it is determined that optimum sintering process and optimum doping concentration.

Result of study shows, optimal sintering temperature is 1300 DEG C, and pottery conductivity is had a significant impact by different levels of doping. But current research work still also exists some problems: one, the people such as M.S.Jang also exists following problem for the preparation technology of GZO pottery: 1. sintering temperature relatively higher (1300 DEG C), sintering time grows (10 hours) partially, therefore, the preparation cycle of this kind of technique is longer, and energy consumption is relatively big, is unfavorable for industrial production. 2. although being equipped with 6 kinds of different componentss, it is determined that best composition (mol ratio is 0.5at%), but pottery lowest resistivity is relatively big, is 1.0 Ω cm. Two, the sintering process of GZO pottery different components (mol ratio 0.5%, 1%, 2%, 3%, 4%, 5%) is mainly studied in detail by the people such as Wu Muying, it is characterized in: under 1200 DEG C, 1250 DEG C, 1300 DEG C, 1350 DEG C, 1400 DEG C, 1500 DEG C, 1550 DEG C sintering temperatures, sinter 2 hours respectively, its optimum sintering condition is calcined temperature 700 DEG C, sintering temperature 1300 DEG C, optimum doping concentration is mol ratio 2%, and the lowest resistivity obtained is 0.1 Ω cm. It is evident that it is longer to there is preparation cycle too, efficiency is low, and energy consumption is relatively big, is unfavorable for the problems such as industrial production, and the minimum specific resistance obtained is still very big.

Summary of the invention

It is an object of the invention under lower doping content (0.075%), it is provided that under a kind of discharge plasma sintering mode, the cycle is short, it is low to consume energy, the optimum sintering process of the GZO pottery of almost completely fine and close and low-resistivity.

The method of a kind of discharge plasma sintering research Ga-doped zinc oxide pottery optimum sintering process, it is characterised in that step is as follows:

(1) by ZnO and Ga₂O₃Ga pressed by powder_0.00075Zn_0.99925O proportioning is placed in and ZrO is housed after weighing₂In the nylon tank that mill is situated between, after taking dehydrated alcohol as disperse agent ball milling 24h, dry, sieving, obtain ZnO, Ga of mixing₂O₃Powder body;

(2) ZnO, the Ga that will mix₂O₃Powder body loads in graphite grinding tool, and compacting, is placed on graphite grinding tool in the furnace chamber of discharge plasma sintering stove, vacuumizes, and pre-pressure is 15MPa;

(3) in 4min, 600 DEG C are risen to from room temperature, heat up with the speed of 10 DEG C/min afterwards, when peak-peak occurs in displacement curve time, pressure is risen to 60MPa, 1100 DEG C are risen to afterwards with 10 DEG C/min heat-up rate, insulation 9min, after cooling terminates, pressure is reduced to minimum, the once sintered one-tenth porcelain of sample.

More specifically realized by following scheme

(1) by high-purity ZnO (99.99%), Ga₂O₃(99.99%) chemical formula Ga pressed by powder_0.00075Zn_0.99925O prepares burden, through ball milling, dry and sieve after, obtain ZnO, Ga of mixing₂O₃Powder body;

(2) using 9min as sintering time, temperature rise rate is 10 DEG C/min, changes different sintering temperatures, sinters a series of sample. Undertaken cutting by the sample after sintering, polished finish, line density of going forward side by side and electrical performance testing, it is determined that optimal sintering temperature;

(3) on the optimal sintering temperature basis determined, change different sintering times, sinter a series of sample. Undertaken cutting by the sample after sintering, polished finish, line density of going forward side by side and electrical performance testing, it is determined that best sintering time, thus obtain the optimum sintering condition of the almost GZO pottery of completely fine and close, low-resistivity.

Compared with the prior art, the obvious advantage of technique of the present invention

(1) adopt discharge plasma sintering mode, tested by system, it is determined that the processing parameters such as optimal sintering temperature and best sintering time, for scientific research and the suitability for industrialized production of GZO pottery provides reference;

(2) relative to existing tradition solid-phase sintering process (general sintering temperature 1300 DEG C～1400 DEG C, soaking time 10 hours), this technique sinter time only at 1100 DEG C time insulation 9min, it is clear that, shorten the cycle of preparation, improve preparation efficiency greatly; Also there is once sintered one-tenth porcelain, the feature that energy consumption is low simultaneously, extremely it is convenient to following industrial production;

(3) this technique is at Ga₂O₃Time doping content lower (weight percent is 0.075%), just having lower resistivity, resistivity is 2.489 × 10^-3Ω cm, and the people such as M.S.Jang are that resistivity during mol ratio 0.5% is only 1 Ω cm in doping content; The people such as Wu Muying are that resistivity during mol ratio 2% is only 0.1 Ω cm in doping content. Obviously, this technique greatly reduces the resistivity of GZO pottery, it is to increase its electric property so that it is have better performance in the application.

Accompanying drawing explanation

Ga when Fig. 1 sintering time is 9min, under different sintering temperature_0.00075Zn_0.99925O powder X-ray RD collection of illustrative plates

Ga when Fig. 2 sintering temperature is 1100 DEG C, under different sintering time_0.00075Zn_0.99925O powder XRD figure is composed

Embodiment

(1) by high-purity ZnO (99.99%) and Ga₂O₃(99.99%) Ga pressed by powder_0.00075Zn_0.99925O proportioning is placed in and ZrO is housed after weighing₂In the nylon tank that mill is situated between, after taking dehydrated alcohol as disperse agent ball milling 24h, dry, sieving, obtain ZnO, Ga of mixing₂O₃Powder body;

(2) loading in graphite grinding tool by powder, compacting, graphite grinding tool be placed in the furnace chamber of discharge plasma sintering stove, vacuumize, pre-pressure is 15MPa;

(3) in 4min, 600 DEG C are risen to from room temperature, heat up with the speed of 10 DEG C/min afterwards, time peak-peak (now the shrinking percentage of sample is maximum) occurs in displacement curve in the computer screen of SPS sintering oven, pressure is risen to 60MPa by (about 720 DEG C), (950 DEG C are risen to afterwards with identical heat-up rate, 1000 DEG C, 1050 DEG C, 1100 DEG C, 1150 DEG C, 1200 DEG C), insulation 9min, after insulation terminates, the knob of control electric current is threaded to minimum, make its Temperature fall, (being generally temperature and be less than 100 DEG C) after cooling terminates is threaded to minimum by the knob of control pressure, pressure is reduced to minimum (being generally 17.5MPa), the once sintered one-tenth porcelain of sample,

(4) powder is become to carry out XRD test part ceramic grinding, again ceramics sample is carried out density measurement, ceramics sample is cut into the square that the length of side is 0.6cm, surface is after polishing, ultrasonic cleaning, indium gallium alloy electrode is put at ceramic plate four angles, carry out Hall effect test afterwards, determine optimal sintering temperature with this;

(5) with reference to the operational path of step 3 and step 4, on the optimal sintering temperature basis determined, change different sintering times (3min, 9min, 15min, 21min), sinter a series of sample. Sample after sintering is carried out the same process of same step 4, and carries out XRD, density and electrical performance testing, it is determined that best sintering time;

Conclusion: the optimum sintering process of Ga-doped zinc oxide ceramic discharge plasma agglomeration method is: sintering temperature 1100 DEG C, sintering time 9min. Under this technique, the electric property of pottery is best.

Table 1 determines optimum sintering process with the pottery of the weight percent 0.075wt% that adulterates

ρ unit: g/cm³γ unit: 10^-3Ω·㎝

N unit :-10¹⁹cm^-3μ unit: cm²v^-1s^-1。

Claims (1)

1. study the method for Ga-doped zinc oxide pottery optimum sintering process with discharge plasma sintering for one kind, it is characterised in that step is as follows:

(1) by ZnO and Ga₂O₃Ga pressed by powder_0.00075Zn_0.99925O proportioning is placed in and ZrO is housed after weighing₂In the nylon tank that mill is situated between, after taking dehydrated alcohol as disperse agent ball milling 24h, dry, sieving, obtain ZnO, Ga of mixing₂O₃Powder body;

(2) loading in graphite grinding tool by powder, compacting, graphite grinding tool be placed in the furnace chamber of discharge plasma sintering stove, vacuumize, pre-pressure is 15MPa;

(3) in 4min, 600 DEG C are risen to from room temperature, heat up with the speed of 10 DEG C/min afterwards, when peak-peak occurs in displacement curve time, pressure is risen to 60MPa, 1100 DEG C are risen to afterwards with 10 DEG C/min heat-up rate, insulation 9min, after cooling terminates, pressure is reduced to minimum, the once sintered one-tenth porcelain of sample.