Author's brief introduction: Lin Fengying, member of the second and third sessions of insurance institute of china Artificial Products Professional Committee, and researcher of Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences.
I. Overview of development
China is rich in rare earth resources, accounting for about 80% of the world's total reserves. The research and development of rare earth materials has broad prospects. 1985 Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (referred to as Shanghai Institute of Optics and Fine Mechanics) has developed rare earth glasses with high optical quality and high refractive index in order to meet the needs of scientific research products such as optical instruments.
From 65438 to 0986, the production of cubic zirconia crystals in Shanghai Institute of Optics and Mechanics stopped due to a series of reasons, such as high power consumption, few colors and unstable quality. In order to replace cubic zirconia gemstone material, a colored rare earth glass with high refractive index was developed by adding colorant to it. We called it "rare earth gemstone glass" and put it on the market at 1988. Because of its rich colors, high refractive index, higher hardness and lower price than ordinary glass, artificial products are very popular as a decoration.
According to the requirements of the market, in the 1990s, we developed a series of rare earth glasses with high chemical stability, which can effectively resist acid and alkali corrosion during electroplating without affecting the quality of the glasses. At the same time, from the perspective of environmental protection, the formula of glass is constantly adjusted and optimized; The original composition contains ≤ 10% PbO. Because lead will pose a threat to human health and the environment, lead oxide is removed, thus an environment-friendly rare earth glass with high refractive index is developed.
At present, more than 60 varieties of rare earth glass have been produced, with a monthly output of more than 3 tons, and can also be produced according to user requirements. In the marketing process of high refractive index rare earth glass, experts in jewelry industry such as Chen Biankun, Shen, Niu Ziran, Zhu Lifu, Zhang Daobiao, Chen, etc. gave great help and support. Over the past 20 years, we have established good cooperative partnerships with national jewelry companies such as Guanghua Company, Orian Company, Oriental Company of Chinese Academy of Sciences, Li Jinde Company, Zongzong Company, etc., and our products are exported at home and abroad, which has opened up broad prospects for expanding the application and export of rare earth materials.
Second, the characteristics of high refractive index rare earth glass
1. High refractive index (n =1.71~1.95)
Rare earth glass with high refractive index is developed on the basis of rare earth optical glass. Rare earth optical glasses, such as lanthanum flint glass (LaF) and heavy lanthanum flint glass (ZLaF), have high refractive index (more than 1.8), high hardness and large dispersion. The synthesized rare earth glass is mainly composed of La2O3-B2O3-Bao-TiO _ 2-SiO _ 2, and a small amount of other metal oxides and rare metal oxides such as ZrO2, ZnO, Nb2O3 and Ta2O3 are added. The refractive index of rare earth glass depends on the main composition of the glass and has a wide range of adjustability. Figures 1 and 2 show the relationship between the partial refractive index and dispersion of each oxide in the glass composition and the cation radius, respectively. It can be seen that the addition of oxides such as La2O3, TiO _ 2, ZrO _ 2, Nb2O3 and TaO 5 can effectively improve the refractive index and dispersion of glass. The refractive index of rare earth glass produced at present is 1.7 1 ~ 1.95.
2. Rich colors and stable quality
Oxides of transition metals, such as titanium, vanadium, chromium, manganese, iron, cobalt and copper, and oxides of rare earth elements, such as neodymium, praseodymium, erbium and cerium, used for high refractive index rare earth glasses are used as colorants alone or in combination.
Because the transition of 4f electrons in rare earth atoms causes selective absorption of optical radiation, its spectral feature is that the edge of multi-absorption band is extremely steep. Therefore, different colors can be displayed under different light sources. For example, glass colored with neodymium oxide (Nd2O3) is red-purple in sunlight and blue-purple in fluorescent lamp, which has a soft and beautiful double color. Because the valence electrons are in the inner layer and shielded by the outer electron layer, the color development is stable. Through the combined use and dosage adjustment of various colorants, as well as the change of the composition of the matrix glass, the color of the glass can be varied and its color can be similar to that of natural gemstones. At present, we have more than 60 kinds of products, such as garnet red (R2, R4), emerald (G 104, G4), olive green (G 107, G 108) and sapphire blue (B2, B 10/08). P6), amethyst (V 102, V 106), golden yellow (Y3), champagne yellow (Y 1, Y2), tanzanite (B30 1), black (BK2) ...
Rare earth glass with high refractive index is produced by optical glass, and high-quality chemical raw materials are melted in platinum crucible at high temperature in electric furnace. Stir during melting, and anneal after pouring. Therefore, there are few striped bubbles in the glass and the quality is stable.
3. Green and environmental protection
After adjusting the formula many times, our existing high refractive index rare earth glass contains neither radioactive elements nor toxic heavy metal element lead, which belongs to green products. The production and processing of rare earth glass with high refractive index will not endanger people's health if they wear jewelry inlaid with this imitation gem for a long time.
4. Good chemical stability, etc
Rare earth glass with high refractive index has excellent oxidation resistance and corrosion resistance, and is not easy to be worn by general objects. But because it is glass, fragile, fragile and not rare, it is usually put on the market as imitation jewelry.
Figure 1 Relationship between refractive index of some oxides and cation radius
Fig. 2 Relationship between partial oxide dispersion and cation radius
Three. Properties of Rare Earth Gemstone Glass with High Refractive Index
199365438+1From October 5th to 9th, the 1st China Gemstone Industry Development Seminar was held in Guangzhou. At the meeting, we announced the properties of high refractive index glass (also known as rare earth jewelry diamond material) for the first time (table 1). At present, the so-called semi-rare earth glass and high refractive index glass matrix artificial gem modified by rare earth elements are actually lead crystal glasses, and the refractive index is usually less than 1.70. For comparison, the related properties of these glasses are also listed in the table.
From the comparison of these data, it can be seen that the performance of high refractive index rare earth glass is obviously better than that of lead crystal glass.
Table 1 comparison of properties between high refractive index rare earth glass and lead crystal glass
Fourthly, the application of high refractive index rare earth glass.
As a artificial gem material imitating natural gemstones and crystals, rare earth glass with high refractive index is welcomed by people because of its bright colors, low price, easy processing and environmental protection. At present, it is widely used in imitation jewelry, fashion jewelry and clothing. With the continuous improvement of national economy and people's living standards, the growing prosperity of personal consumer goods market and the increasing requirements for health and environmental protection, high refractive index rare earth glass will also have better development opportunities and broader market prospects.
refer to
Gan Fuxi et al. 198 1. Physical properties calculation and composition design of inorganic glass. Shanghai Shanghai Science and Technology Publishing House.
Gan Fuxi et al. 1982. Optical glass. Beijing: Science Press.