Lead-Zirconate-Titanate Powder Preparation

Hydrothermal Method: In the first stage zirconia/titania mixed gel is prepared from the solutions of ZrOCl₂ and TiCl₄ by mixing ammonia solution. The prepared solution contains high concentration of ZrOCl₂ and TiCl₄. In this a 10% excess of PbO and a mineralizer of alkali halides and hydroxides are added.

The mixture is hydrothermally treated at about 300^.C under a pressure of 7 to 8 MPa in a auto clave. After hydrothermal reaction the product is cooled and washed with 10% acitic acid solution and finally washed to get neutral ph. The particles produced is of very pure and having very high surface area with sub micron size.

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Lead-Zirconate-Titanate Powder Preparation

Coprecipitation Method: The ZrOCl₂ solution and TiCl₄ solution is mixed along with the addition of ammonia solution with a ph of 7 to 8. The mixing results in a precipitate. The precipitate formed is washed and nitric acid is added so as to form Zr, Ti-nitrate solution.

To the Zr, Ti-nitrate solution Pb(NO₃)₂ is mixed to form a composite solution of Pb,Zr, Ti-nitrate solution and it is sprayed into a large volume tank having agitated bath of alkaline ammonium nitrate solution.

During the precipitation process the temperature has to be maintained between 55 to 60^.C with controlled ph of 7 to 8. The precipitate is repeatedly washed with actone during de watering. The washed precipitate is calcined at about 650^.C to form high purity, nano particle size particle and non-agglomerated PZT powder.

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Lead-Zirconate-Titanate Powder Preparation

Lead-zirconate-titanate powder is a very important Advanced Ceramic Raw Material used in various high end applications of Advanced Ceramics. There are two types one is anti Ferro electric lead zirconate (PZ) and the other is Ferro electric lead titanate (PT) and the combination is called PZT.

This combination form a series of solid solutions which exhibit piezo-electric properties required in electronic applications. The most favourable compositions are either zircon rich phase or titania rich phase. The addition of dopants like Nd, La etc. Influences the sintering behaviour and modify the desired electrical properties of the PZT powder.

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Lead Titanate Powder Preparation

Hydro thermal Method: In this method oxides or hydrous oxides obtained from nitrates, acetates, chlorides, per chlorates or alkoxides may be used as sources of led and titanium. The hydro thermal reaction happening in the temperature range of about 200 to 300^.C is very important in this method.

The reaction is done in a stainless steel auto clave at a pressure of 1.75 to 9.48 MPa. Lead titanate powder formed in the auto clave is washed with ammonia water and dried in a dryer. The powder formed is of very high pure in nature and the particle size below submicron size.

Lead Titanate Powder Preparation

There are two chemical preparation route for preparing Lead Titanate Powder of homogeneous in character and particle size less than one micron.

• Co precipitation Method
• Hydro thermal Method

Co precipitation Method: In this method precipitating precursors of lead nitrate and titanium tetra chloride solution are used apart from liquid ammonium. To prevent the formation of lead chloride a small quantity of ammonium nitrate is added to the mixture. Hydrogen peroxide solution is added for facilitating the precipitating reaction. Precipitation of lead titanate will happen at about 65^.C. The ph is maintained between 8 to 9.

In the next stage the washed precipitate pyrolysed at a temperature of about 500 to 800^.C so as to form Lead titanate Powder of nano particle size with very high surface area.

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Strontium Titanate Powder Preparation

Spray Pyrolysis Method – Spray Pyrolysis Method otherwise called as Aerosol Decomposition Method is a potential promising method for preparing chemically homogenous multi component powders with controlled morphology and particle size distribution. This process technique is purely based on the intra particle reaction for chemically homogenous multi component powder preparation.

The preparation system involves an aerosol generator where precursors are dissolved in a suitable solvent. In the next stage a carrier gas is passed through the aerosol generator. The precursor solution atomized by using an atomizer followed by passing through a reactor at a temperature of about 800 to 1100^.C. During heating the solvent evaporate and the precursors decompose and react to form the product.

By this process agglomerate free Strontium Titanate particles of submicron size with high surface area can be prepared.

Strontium Titanate Powder Preparation

Solvent Vaporization Method:

Freeze Drying Method — In the first stage the stable complex of titanium citrate is prepared by mixing titanium tetra isopropoxide with citric acid and deionzed water at about 70^.C. The solution is mixed with ammonia solution by adjusting the ph to 5 to 6. The concentration of titanium is increased by boiling the solution with simultaneously removes the isoporpanol by product.

Strontium nitrate solution is added to the above solution so as to form strontium titanium solution. This solution sprayed into liquid nitrogen as a mist for rapid freezing. Thus freeze drying of the product at -60^.C causes the removal of water from the solution by sublimation process.

In the next stage the product formed is heated in a controlled atmosphere a temperature of 700^.C for few hours. After heating it generates spherical strontium titanate powder with very high surface area.

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Strontium Titanate Powder Preparation

Complex Precursor Method: In ethylene glycol solution tetra-n-butoxy titanate is added and heated at about 75^.C for fifteen minutes under continuous stirring so as to form a mixture of the above two components. To this mixture citric acid is added while heating the mixture to a temperature of about 85^.C.

This reaction forms a clear yellow solution. Strontium nitrate is dissolved in the yellow solution to form the precursor solution. The precursor solution on further heating about 550 to 700^.C for an hour forms strontium titanate crystals. The product formed through this process is homogeneous in nature and the surface area of the particle is very high.

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Strontium Titanate Powder Preparation

There are various methods available for preparation of strontium titanate powder and the more important chemical methods are given below

• Alkoxide Method
• Complex Precursor Method
• Solvent Vaporisation Method

Alkoxide Method

Mixture of recrystalised strontium iso-propoxide and distilled Titanium pertiary amyloxide is stiochaometrically refluxed at 85^oC for 5 to 6 hours. This reaction forms the complete miscibility of the alkoxides. In the next stage the decomposition is carried out under controlled conditions so as to form Strontium Titanate.

The powder obtained in this process is further dried in a flow of helium gas at about 110^oC. This process produces nano particle size Strontium Titanate Powder with high surface area.

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Barium Titanate Powder Preparation
Hydrothermal Synthesis Method

TiOCl₂ and BaCl₂ are treated in Sodium Hydroxide solution at about 120 ^oC to 300^oC under pressurization of 5 to 50 Bar Pressure. This hydrothermal reaction produces barium titanate powder. Normally the stoichiometry is not maintained due to excess titanium. To maintain the stoichiometry the synthesis is therefore carried out in the presence of large excess of barium.

The reaction temperature for precipitation process is very low and hence it is possible to produce unagglommerated, sub micron and uniform size spherical Barium Titanate Powder by the Hydrothermal Synthesis Process. This method also make the powder sinterable at a relatively low temperature of 100^oC to 200^oC