Application of laser particle size analyzer in barium titanate particle size detection (1))

1. Barium titanate and its industry development

   Barium titanate is a strong dielectric compound material with high dielectric constant and low dielectric loss. It is one of the most widely used materials in electronic ceramics and is known as the "backbone of the electronic ceramics industry."

Barium titanate, also known as barium metaacid, is soluble in concentrated sulfuric acid, hydrochloric acid and hydrofluoric acid, but insoluble in hot dilute nitric acid, water and alkali. Barium titanate currently has five shapes, namely: square crystal form, cubic crystal form, cocubine crystal form, trigonal crystal form and hexagonal crystal form. The most common is the square crystal form. In the production of ferroelectric ceramics, the hexagonal crystal phase is a phase that should be avoided. In fact, the hexagonal crystal phase will only appear when the firing temperature is too high.

Barium titanate is the main raw material for the preparation of many dielectric and piezoelectric materials such as ceramic capacitors and thermistors. In recent years, with the rapid development of the ceramic industry and electronic industry, the demand for BaTiO3 will continue to increase, and its demand for BaTiO3 will continue to increase. Quality requirements are also getting higher and higher. Preparing high-purity, ultra-fine powder materials is the main way to improve the performance of electronic ceramic materials. Therefore, the research on the preparation of high-purity, uniform, ultra-fine and even nanometer barium titanate has always been the research focus of scientists from various countries.

Barium titanate is the basic parent material of electronic ceramic components and is called the backbone of electronic ceramics. Because of its good ferroelectric, low-voltage, withstand voltage and insulation properties, it is widely used in the production of high-capacitance capacitors, multi-layer substrates, various sensors, semiconductor materials and high-sensitivity components. With the rapid development of electronic components towards high integration, high precision, high reliability, multi-function and miniaturization, higher requirements have been put forward for the preparation of barium titanate materials that meet performance requirements. The preparation and research of nanometer barium titanate has become a research hotspot.

The preparation research of nanometer barium titanate powder has always been a hot spot in the field of science and technology. Various preparation technologies have been greatly developed. With the increasing emphasis on barium titanate electronic ceramics, the size, uniformity, and The requirements for various aspects such as purity and similarity of the chemical properties of the final product are also getting higher and higher. Therefore, it is necessary to conduct in-depth research on the process mechanism of synthesizing barium titanate powder, and to control the shape, size, performance and other technologies of the particles. The relationship between them should be discussed in more depth; the current results are mostly in the laboratory and small-scale production stage, and the issues involved in large-scale production should be studied; the currently used nano-barium titanate particle synthesis device needs to be improved, In particular, there is a need to develop industrial equipment with high productivity, high output, high quality and low cost. Based on the improvement of preparation methods, the broadening and deepening of research methods, and the close cooperation between materials science, physics, chemical engineering and other disciplines, it is believed that nanobarium titanate will show broad and attractive prospects in the electronics industry and ceramic industry.

2. Preparation of nanometer barium titanate

Barium titanate is a classic ferroelectric and piezoelectric ceramic material. Due to its high dielectric constant, good ferroelectric, piezoelectric, voltage resistance and insulation properties, it is mainly used to make high-capacitance capacitors, multi-layer substrates, Various sensors, semiconductor materials and sensitive components. With the rapid development of modern science and technology and the miniaturization and high integration of electronic components, it is necessary to prepare and synthesize high-quality barium titanate-based ceramic powder that meets development requirements. Therefore, research on the preparation of high-purity, uniform, ultrafine and even nanometer barium titanate has always been the research focus of scientists from various countries. Based on the improvement of preparation methods and the broadening and deepening of research methods, the preparation of nanobarium titanate has also entered a new stage.

Since the ferroelectricity of barium titanate was discovered in the 1840s, various countries have begun to study the synthesis and preparation of barium titanate. The liquid phase method effectively controls the microstructure and properties of the powder during the production process of barium titanate using physical and chemical methods. Since the 1980s, the liquid phase method has gradually become a method generally valued by various countries, and has gradually developed into the three most important methods. : Precipitation method, sol-gel method, hydrothermal method.

    The precipitation method has the advantages of simple method, low material cost and low equipment investment. Doping elements can be added during production to directly produce a certain formula of powder raw materials, which is most suitable for the manufacture of ceramic components. The precipitation method is a widely used method for industrial production of barium titanate powder, and it is also the first commercial production method. However, this method also has some shortcomings. For example, it is difficult to obtain nanopowders with very small particle sizes. The particles are easy to agglomerate and have a wide particle size distribution, which requires certain post-processing. The synthesized powder changes slightly with the reaction conditions, titanium and barium. The specific fluctuation is large and the product quality is unstable.

Due to the special reaction conditions, the powder prepared by the hydrothermal method has the advantages of small particle size, uniform distribution, and less agglomeration, and its raw materials are easier to obtain products that meet the stoichiometric ratio and have a complete crystal form; at the same time, the powder does not require high temperature The calcination treatment avoids grain growth, formation of defects and introduction of magazines, and has higher sintering activity. However, either the BaTiO3 synthesized in these works has a metastable cubic phase structure instead of a tetragonal phase, which cannot meet the performance needs of electronic components; or the water heating requires high temperatures and long times, resulting in excessive equipment costs; or water heating Thermal synthesis requires the use of organic titanium as raw material, which results in high equipment costs, or hydrothermal synthesis requires the use of organic titanium as raw material, which results in high production costs. These reasons make it impossible to achieve large-scale production of hydrothermal synthesis of tetragonal phase BaTiO3 nanopowder. At the same time, the hydrothermal method contains impurities in the powder, which also limits the application of this method.

     The sol-gel method often uses distillation or recrystallization technology to ensure the purity of the raw materials. No impurity particles are introduced during the process, and the resulting powder has a small particle size, high purity, and a narrow particle size distribution. However, the raw materials are expensive, the organic solvents are toxic, and the high-temperature heat treatment will cause the powder to quickly agglomerate. The reaction cycle is long, the process conditions are difficult to control, the output is small, and it is difficult to scale up and industrialize. .