Bismuth Sodium Titanate Spray Pyrolysis for Stoichiometry Control
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Solution Overview
Problem
Existing methods for producing bismuth sodium titanate (BNT) ceramics face challenges such as high calcination temperatures leading to volatile element loss, uncontrolled stoichiometry, and the need for harmful solvents, making large-scale production difficult.
Innovation Solution
A spray pyrolysis technique using a dual phase nozzle arrangement to produce BNT compounds, ensuring atomic-scale homogeneity and low-temperature treatment, resulting in fine-grained, dense ceramics with controlled stoichiometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high calcination temperatures are used to react bismuth oxide, sodium carbonate and titanium oxide, then the materials can be synthesized, but high vapor pressures cause loss of Bi and Na cations and uncontrolled non-stoichiometric compositions
Solution Approach 1:
The invention changes the temperature parameter from high calcination temperatures (800-1000°C) to low-temperature treatment (600-800°C) after spray pyrolysis. This parameter change allows the formation of BNT powder with controlled stoichiometry at lower temperatures, preventing the vapor pressure-induced loss of volatile Bi and Na cations that occurs at high temperatures
Solution Approach 2:
The spray pyrolysis process performs preliminary action by pre-forming the BNT powder with controlled stoichiometry and homogeneous cation distribution before the final low-temperature treatment. This preliminary formation at controlled conditions prevents subsequent loss of volatile elements during heat treatment
2Temperature
If high calcination temperatures are used to react the materials, then the materials can be synthesized, but uncontrolled non-stoichiometric compositions result
Solution Approach 1:
The invention changes the temperature parameter from high calcination temperatures to low-temperature treatment (600-800°C) after spray pyrolysis. This parameter change enables precise stoichiometry control because the low temperature prevents excessive diffusion and volatilization that would lead to uncontrolled non-stoichiometric compositions
Solution Approach 2:
The invention replaces the mechanical mixing and high-temperature reaction process with a solution-based spray pyrolysis method. This substitution allows atomic-scale homogeneity and precise stoichiometry control because the metal ions are already uniformly distributed in the solution before pyrolysis, eliminating the need for high-temperature solid-state reactions
3Ease of manufacture
If alternative solution based production methods are used, then production can be improved, but harmful or flammable solvent systems are required
Solution Approach 1:
The invention changes the solvent parameter from harmful or flammable organic solvents to water as the solvent system. This parameter change maintains the advantages of solution-based production (atomic-scale homogeneity, low-temperature processing) while eliminating the harmful and flammable properties of organic solvents
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process enables the production of high-quality BNT powders suitable for ceramic processing, achieving electromechanical performance comparable to state-of-the-art materials, suitable for large-scale production without toxic solvents.
Implementation Method 1
spray pyrolysis of a solution comprising Bi ions, Na ions, Ti ions and, if present, metal (A) and/or metal (B) ions
Implementation Method 2
spray pyrolysis is carried out using a dual phase nozzle arrangement
Data Source
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AI summary
The invention provides a process for the preparation of a bismuth sodium titanate (BNT) compound of formula (I) wherein A is one or more of Bi, Na, Li, K, Mg, Ca, Sr, Ba, La, Al, Cu, Eu, Ag and Zn; B is one or more of Ti, Nb, Ta, Zr, Fe, Nd, Eu and Co; 0 < x < 0.8; 0 <y < 0.8; and -0.1 < z < 0.1; said process comprising spray pyrolysis of a solution comprising Bi ions, Na ions, Ti ions and, if present, metal (A) and/or metal (B) ions.