Research progress of rare earth ion characteristics and rare earth functional materials
Rare Earth (RE) is a group of 17 metal elements formed by Group III (SC, Y) and lanthanum (La-Lu). Rare earth elements are usually divided into two groups, namely cerium group (light rare earth) and yttrium group (heavy rare earth). Rare earth elements show very similar properties, that is, they generally have + 3-valent oxidation states under environmental conditions and have large electropositivity and dynamic stability. According to Pearson’s hard acid and soft acid-base theory, the lanthanum (Ln) ion is a hard Lewis acid . RE has a unique 4D valence electron structure, which makes RE have excellent optical, electric, magnetic and catalytic properties . Understanding the characteristics of rare earth ions, such as the electronic transition of Ln elements, spin coupling and orbital hybridization, etc., can reasonably design various chemical reactions to synthesize or prepare the target compound, so as to find new functional materials .
The orbital hybridization mode of Ln elements illustrates their chemical bond properties in all reaction systems. The wide coordinate number (CN) selection ranges from 2 to 16, which is the reason why Ln element has become a new material Treasure House . The rare earth element is introduced into the crystal structure as one of the lattice points is called the rare earth crystal, and its size is beyond the completeness of the structure and the difference in composition, RE ions can be used to improve the physical and structural properties of matrix compounds, and even find novel material properties . Compared with non-doped compounds, rare earth compounds have unique properties, and their key attributes include new emission characteristics, enhanced stability, reduced defect state density or passivated grain boundary, etc. Therefore, rare earth elements are the key components of emerging science and technologies such as energy conversion, catalysis, magnetism, photonics, superconductivity, quantum engineering, etc. As one of the key strategic materials, rare earth functional materials are the important material basis for the realization of the strategy of innovation-driving development of strategic emerging industries. They can be divided into rare earth optics, magnetism, electricity and other new materials, as shown in scheme1, with rare earth elements as the core, it is composed of rare earth oxides, alloys and various salt compounds, with a total of 30 functional crystal materials, topological insulators play an important role in new fields such as strong light lighting.
Scheme 1. Rare earth functional materials can be divided into rare earth optics, magnetism, electricity and other new materials. There are a total of 30 kinds of crystal materials, which play an important role in new neighborhoods such as laser refrigeration, magnetic refrigeration, topological insulators and strong lighting
Rare earth ion characteristics
Table of Contents
- Rare earth ion characteristics
- Rare earth functional materials
- Conclusions and prospects
Bonding characteristics of rare earth ions
Rare earth elements generate chemical compounds with other elements through chemical reactions, so as to produce new chemical bonds that make up the elements. Understanding the chemical bond properties of rare earth elements is the key to find new functional materials for rare earth, the chemical bonding ability depends on the different coordination environments, I .e., 4f0-145d0-16s2 valence electrons . In order to reveal the unique chemical bonding characteristics of the lanthanum element Ln), the role of the 4fvalence electron and the 4forbit in the chemical bonding should be clarified first. In the lanthanum, the 4fshell radially shrinks as the atomic number increases, and the space range of the 4forbital is small, which limits the overlap with the ligand orbital, whether Ln’s 4f orbital is involved in any bonding with its ligand, or to what extent it is involved in bonding, has always been the subject of theoretical and experimental research . Through quantitative analysis of atomic electronic domains , it is found that the chemical bond characteristics of 4felectrons are hybrid, and they are divided into sp, when the coordination numbers of the three hybrid types of chemical bonds, sp d and sp df, are determined to be 2~4, 5~9 and 10~16 respectively, it can be obtained that when the coordination number of rare earth ions is more than 9, only in this way can it be determined whether the falling electrons can participate in chemical binding.
Electronegativity scale of rare earth ions
Electronicity (En) is the scale of the electron attraction ability of the atom of the element in the compound. In the Pauling scale, En is usually regarded as the constant factor of the atom, but this depends on the valence of the ion, coordination numbers and structural features . According to the effective ion potential defined by ionization energy and ion radius, the electronegativity of rare earth elements under different valence states and the most common coordination digit is quantitatively calculated . The results show that the relative value of electronegativity can reflect the stability of the ligand field 、p the first filling of the orbital and the contraction of the lanthanum system. En is also an important theoretical basis for chemical bonds and material design. Two groups of En scales  are established according to the electrostatic potential of atomic in rare earth crystals. After considering the actual chemical environment of atoms in detail, en scale is used to predict the chemical and physical properties of crystals and further design new rare earth functional materials.
Luminescence characteristics of rare earth ions
The rare earth ions have abundant energy levels and the transition of 4f electrons, among which, the 4f electrons of the remaining lanthanum ions except for La3 + and Lu3 + can be distributed arbitrarily between 7 4f orbits, thus various spectral terms and energy levels are generated. As many as 30000 spectral lines can be observed for atoms or ions of the unfilled f electron shell. Therefore, various wavelengths of electromagnetic radiation from ultraviolet to infrared can be emitted, and as the luminescent center of the material, rare earth optical crystal materials have excellent luminescent properties. The change of energy transfer efficiency between rare earth ions and ligand energy level structure can regulate the luminescent properties of the complex . The luminescence of the up-conversion material originates from the electronic transition in the hao orbit configuration of the lanthanum ions. The difference in the size of the doped ions will affect the coordination environment in the matrix, resulting in the formation of asymmetric crystal fields, promote the mixing of the 4fenergy level of the lanthanum ion with a high electronic configuration, thereby improving the up conversion luminescence rate . Different from the traditional typical luminescence process (which only involves one base state and one excited state), the transition process requires many intermediate states to accumulate the energy of the low-frequency exciting glow. There are mainly 3 kinds of light mechanisms: Excited state absorption, energy conversion process , Photon Avalanche , these processes are all achieved by doping in the crystal particles with a large number of rare earth activated ion energy levels of substable energy level to continuously absorb one or more photons. In rare earth scintillation materials, rare earth ions act as the center of scintillation, and the content of rare earth elements affects the fluorescence lifetime and luminous intensity .
In rare earth fluorescent materials, the concentration of rare earth ions increases and the fluorescence intensity gradually enhances, but with the increase of the number of rare earth ions luminous centers and their closer distance, the probability of no radiation transition between the ions themselves increases, concentration quenching occurs when the luminescence intensity is reduced . In order to study high-power and high-strength lighting materials, the important problem is the effect of increasing temperature on the luminous intensity of phosphors. For example, zero heat quenching in Na3-2xSc2 (creativity) 3:xEu2 + blue fluorescent powder , this phenomenon can be explained from the perspective of the polymorphism modification of the electron hole of the heat-activated defective energy level to the Eu2 + 5d band and the possible energy transfer, therefore, the fluorescent powder can maintain the luminous intensity when the temperature rises. Looking for the development and optimization strategy of new fluorescent material matrix can not only be designed from the level of rare earth ions, but also be based on the mineral structure model, namely garnet, apatite and yellow feldspar structure to design rare earth fluorescent materials .
In conclusion, the rare earth luminescent materials mainly depend on the electron transition of the rare earth ions. As shown in figure 1, the display on the left side shows the process that the inter-band transition corresponds to the excitation of electrons from the top of the valence state to the exciton state. These transitions provide information about the basic absorption threshold and the position of the mobility edge or the bottom of the conduction band. The left second shows that electron transfer between the two lanthanum elements is possible when both are present simultaneously. One is a lanthanum element that acts as a donor, and the other acts as a receptor, both of which change the valence during the transition period. Electrons are transferred from lanthanum to host bands and vice versa to cause changes in the valence of the lanthanum element. The third on the left shows that when the ground state of the lanthanum element is in the forbidden band prior to its transfer, it can act as the electron donor of the conductive band or the hole acceptor of the valence band. Similarly, when the ground state after transfer is in the gap, the lanthanum element can act as an electron acceptor or a hole donor. The far right display shows two types of internal electron transitions that can be distinguished: internal configuration 4fn-4fn and internal configuration 4fn-fn-15d transition .
Figure 1. Four different types of electronic transitions in lanthanide-activated compounds.Ex means the energy needed to excite electrons from the top of the valence band through the band gap to form excitons. Ec and Ev are the energy of the minimum conduction band and the maximum valence band, respectively
Magnetic properties of rare earth ions
Magnetism is an objective physical phenomenon in which substances are affected by static magnetic force in non-uniform magnetic field. In principle, all substances have some kind of magnetic characteristics corresponding to their thermodynamic conditions. According to the different magnetic behaviors of the substance in the magnetic field, the magnetism can be divided into ferromagnetic, ferromagnetic, antiferromagnetic, paramagnetic and diamagnetism. Due to the large atomic number of rare earth elements, amorphous alloys such as Gd, Dy, Tb and Ho have rich magnetic structure and good thermal stability. In rare earth magnets, single-ion physics plays a leading role in the exchange interaction between two ions, showing a fairly clear level of energy level, and the coulun interaction dominates spin-orbit coupling, influence of spin-orbit coupling-dominated Crystal environment. The base state of a free ion is obtained from the minimization of the energy of the coulometric energy and the spin orbit .
The rare earth element is located in the 4x region, and there are many unpaired electrons. For example, the 4f7gd element has 7 unpaired electrons. Therefore, the magnetic properties of rare earth depend on the nature of the 4forbit, the interaction between these orbits and the environment is very weak, and the magnetic properties of electrons are determined by spin and orbital components. Spin is isotropic, and the orbital component reflects the symmetry of the system and can be anisotropic. For f electrons, the orbital moment is largely non-quenching, so the magnetism is highly anisotropic. For example, dysprosium (such as Dy), which is the alloy with iron and terbium, has the highest electrostriction at room temperature . Some rare earth compounds (such as cerium-doped phosphates) have a high magneto-optical rotational ability . Rare earth compounds have superior magnetic properties, but their Ree temperature is relatively low, and Fe, Co and Ni are higher than rare earth. Gd is the only rare earth metal that has ferromagnetic properties at room temperature, and 58Ce-62Sm is anti-ferromagnetic substance; 63Eu-69Tm is ferromagnetic .
The structure of 3 types of G anti-ferromagnetic spin of Ln FeO3 type rare earth positive ferrite (Ln G d,Dy Sm) is shown in figure 2. In the exchange interaction between Fe 、Ln- Fe and Ln-Ln, Fe Fe has the strongest order, resulting in the anti-ferromagnetic dip order of Fe sublattice at 650~700 K . The relatively weak Ln-Fe interaction leads to the polarization of Ln sublattice in the weak ferromagnetic moment exchange field. The anisotropic properties of Ln and Fe magnetic moments cause two magnetic phase transitions with temperature: spin reorientation and temperature-induced magnetization reversal are below the compensation point, the rare earth magnetic moment and the weak ferromagnetic moment of Fe sublattice are anti-ferromagnetic coupling. At low temperature (<10 K), Ln-Ln interaction leads to anti-ferromagnetic order of rare earth ions. Orthogonal ferrite with non-magnetic Ln ions shows only the Left spin structure of figure 2 at all temperatures. In fact, spontaneous polarization occurs when Néel temperature of GdFeO3 compound is 241 K , while in DyFeO3, in the presence of magnetic field, ferroelectricity was found at the antiferromagnetism of Dy3 + ions .
Figure 2. Ln FeO3-type rare earth ferrites (Ln =Gd, Dy, Sm) exhibit three types of G-type antiferromagnetic spin structures on the Fe site. Fe and Ln are represented by spheres with and without spins respectively 
Electrical properties of rare earth ions
Rare earth elements have a special 4f5d electronic structure, and the variability of their coordinates determines that they have a certain “back-up chemical bond” or “residual atomic valence, rare earth ion doping can improve the crystal structure of rare earth electrical materials, improve conductivity and reduce ion diffusion resistance . For example, in topological insulator, Sm doping changes the crystal structure and electronic structure of Sm 0.1Sb1.9Te3 , thereby improving its magnetic transport characteristics. Since the magnetic moment of the rare earth on the 4felectron is shielded and orbital moment is allowed to exist, the doping of rare earth element may generate inherent ferromagnetism, and magnetic moment can lead to the formation of band gap in topological insulator, in which the size of gap is proportional to magnetic moment, therefore, there is a hope to find a ferromagnetic topology insulator with wide bandwidth. The nanoscale structural heterogeneity introduced by doping strategy further enhances the piezoelectric effect of Pb(Mg1/3 Nb2/3)O3-PbTiO3(PMN-PT) , doping of rare earth elements can introduce effective random fields (bonds) and/or change the order degree of B- position cation, enhance the local structural heterogeneity of PMN-PT, and further enhance its dielectric and piezoelectric properties. The material of the ferrite has macroscopic and switchable polarization, and can be controlled by external electric field. The ferroelectric polarization is shown in Fig. 3.
Figure 3. Ferroelectric polarization originates from the asymmetric distribution of atoms in the crystal structure of the material-positively charged and negatively charged ions move slightly from symmetrical distribution to the opposite direction, due to the presence of unpaired ions, the ferroelectric surface is negatively or positively charged
Even in functional materials of the same structure, the mechanism of compounds of different components is caused by different reasons. For example, the dielectric property of rare earth double ferrite Sr2ErNbO6 has obvious frequency dispersion. At 100Hz, with the increase of temperature, the conductivity increases. The analysis shows that, the conductive mechanism is caused by ion transition . The conductive mechanism in Sr2CeSbO6 compounds is due to electron transition .
Characteristics of rare earth ions in new functional materials
Rare earth elements have rich energy level and soft electron transition characteristics, easy to produce multi-electron configuration, have special optical properties, and can be used in crystal structure, energy band structure, light absorption performance, the surface adsorption performance and other aspects of the photocatalyst matrix material are modified, at the same time, many new photocatalyst systems can be constructed, and their oxides (zeo2) also have photocatalytic effect (Figure 4d). Rare earth elements, as a group of similar but different elements, provide material for the study of the influence mechanism of the electronic structure, valence, ion radius and other factors on the properties and performance of photocatalyst. Rare earth elements can not only improve the catalytic performance in the organic system, for example, La modified y-type molecular sieve can enhance the catalytic activity , but also enhance the catalytic characteristics in inorganic compounds, for example, in la2ni-4 compound , the valence shell of the compound is established by 6s and 1 5d electron, and the additional d electron in the valence shell leads to the polarization of 6s valence orbit. Therefore, la can promote chemical adsorption of oxygen and make oxygen molecules unstable by surface-to-molecular charge transfer, indicating that since the electronic configuration of surface species on adjacent La locations is enhanced, this surface has catalytic activity.
Figure 4. (a)Distorted perovskite structure of SNO crystal. (B )Conventional solid electrolytes (A、 B and M are metal cations, and O is the proton incorporation and conduction m echan m in the oxygen anion) and (c)the proposed new electrolyte. (d)The role ofrare earth ions in photocatalysis
Besides it has catalytic performance , it can also be used as electrolyte. SmNiO3(SNO) a rare earth nickel acid (RNiO3) belonging to the ferrite structure, BO6 octahedron shared by connected angles (fig. 4a). In the ferrite oxide, protons can form ionic defects through binding to oxygen and diffuse through the Grotthus Mechanism, this involves rapid rotational diffusion of proton defects and the transfer of rate-limited protons to adjacent oxygen ions. Transition States of proton rotation and proton transfer require local lattice distortion respectively, such as the elongation and bending of B- O bonds . A schematic diagram of the process of cubic-roman proton binding and diffusion, as shown in fig. 4b, includes the following processes: proton binding to rotary diffusion, transfer to adjacent oxygen, bending and B- O the elongation of the bond .
Rare earth functional materials
The shielding properties of the ptfe orbit of the rare earth lead to a clearly defined energy level, which is subject to weak interference from the environment and accompanied by greater spin-orbit coupling, this allows RE to be applied in optical and magnetic applications. As shown in Fig. 5, optical, magnetic and electrical properties have been developed in some research fields.
Figure 5. Classification of rare earth functional materials
Lanthanum-doped nano-and micro-ceramics play an important role in the field of modern lighting and biomedical imaging due to their unique optical and chemical properties . Solid-State cooling technology is an environment-friendly, energy-saving and scalable technology, which can solve most problems in current refrigeration methods. It relies on the cyclic application of external lasers, magnetic fields, electric fields or mechanical fields to compounds of rare earth materials. Due to field-induced phase changes, these compounds undergo temperature changes. For example, because of the E4 →e5 crystal field transition of Yb3 +, the crystal of high purity YLiF4 doped with mole fraction of 10% Yb3 + is cooled to 91 K after being stimulated by laser at 1020 nm, and an all-solid-state optical refrigerator is made . Magneto-thermal effect refers to the thermal change generated by the material under the action of magnetic field, and since the magnetization/demagnetism of the magneto-thermal material is reversible, an efficient cooling device can be established in the thermodynamic cycle . Rare earth metal organic framework materials have potential application value in cryogenic magnetic refrigeration .
Rare earth-based permanent magnet material is another important application of rare earth elements. So far, many material systems have been explored, such as Nd B/Fe (Co)、SmCo/ Fe(Co), etc, it includes thermal deformation , plastic deformation , self-assembly  and from-down-up . Currently, permanent magnets are based on Nd2Fe14B, which is a complex metal system . It is crystallized in the square crystal structure of P42/mnm, in which Nd atoms occupy 4fand 4g positions, and Fe occupies 6 different atomic positions (16 k1, k2 16, 8 j1,8 j2,4e,4c), while B only occupies 4G bit . Permanent magnet is the key component of many devices, from motor to micro speaker disk drive automobile traction motor, to the wind generator.
The material that transfers electric energy with 100% efficiency is called superconductor. They have a wide range of applications, such as hospital magnetic resonance imaging. However, these applications are hindered, mainly because the superconducting state only exists at temperatures far below room temperature. Drozdov et al.  reported that when the pressure is compressed to 1 × 106 times that of atmospheric pressure, the H-rich hydrogenated lanthanum (La H) compound will be superconductivity at 250 K. It can be expected that room temperature superconductivity may be realized in the near future.
Rare earth functional materials can not only be applied to the development of devices, but also promote the research in the aspect of theory, for example, physicists put forward the concept of time crystal based on the concept of breaking time translation symmetry, opening up a new research field, using a pair of raman laser beams to illuminate the entire 171Yb + ion chain to drive qubits rotation, the experimental observation results of discrete-time translational symmetric broken discrete-time crystals are given, and the continuous oscillation and synchronization of the mutual spin in the chain are measured, indicating that the discrete-time crystals are rigid, or Robust to disturbances in the drive .
As shown in the figure, the rare earth functional materials can be divided into optical, magnetic, electrical, catalytic and energy storage, which are composed of oxides, hydride, oxygen-containing salts, alloys, etc. Rare earth functional crystal materials can also be divided into one-element, two-element, ternary and multi-element rare earth functional crystal materials according to their composition. Unary material is composed of a single rare earth element, for example, multiple cravity has a strong influence on the base state spin configuration of Ho at 50 K, the possible reason is due to the relevant changes in material energy scale . Binary rare earth materials are composed of two elements, including binary rare earth alloy , rare earth-transition metal compound and other binary rare earth compounds, which are widely used as superconductor, catalytic materials, etc. For example, in the research of finding superconducting materials at room temperature, materials rich in hydrogen and carbon can provide high frequency and strong electron-phonon interaction required in phonon spectrum, of which hydride family has a cage structure, rare earth ions are located in the center of H24 cage and act as electron donors to promote electron pairing, while hydrogen atoms form weak covalent bonds with each other in the cage. These super hydride can be regarded as a further realization of metallic hydrogen, so it has a higher critical temperature (Tc) value. Currently, lai10 with a critical temperature of 250 K is reported . When a trivalent rare earth ion is inserted into CeO2, the emission of the doping substance can be excited through direct excitation or sensitization absorption of the host . However, due to the presence of oxygen vacancy, the best sensitizer is not CeO2, but the f-d transition dispersed on Ce3 + ions. Considering the indirect excitation process of Ce3 + ions, at least a part of these trivalent rare earth ions migrate to ceo2. 4 f2F7/2 excited state relaxation of Ce3 + is conducive to the down conversion process.
Figure 6. Rare earth functional materials are composed of oxides, nitrides, oxygen-containing salts, etc
Ternary materials, that is, rare earth functional materials composed of three elements including rare earth elements include rare earth transition metal compounds, composite rare earth halides, ternary rare earth oxygen-containing salts, etc. For example, Al2O3 has excellent thermal conductivity (k ~30~35 W/( m · K-1) and thermal shock resistance (Rs ~ 19500W/m) with high fracture toughness (3.5 M Pa/ m 1/2), alumina can be effectively emitted at other wavelengths by adding rare earth elements to the concentration of gain, thus, a laser gain medium with thermal, mechanical and optical properties is formed, thus bringing stronger laser for scientific, medical, industrial and mobile applications . As the ideal matrix of typical geometric frustration, the material with coke structure (A2B2O7), whether it is the classical spin ice or the quantum spin liquid behavior, is the subject of extensive research in the field of magnetism. The explanation for the magnetic behavior of Yb2Ti2O7 is originated from the Yb3 +(4 f13) ion  that forms A sublattice, in the ideal Yb2Ti2O7 stoichiometric ratio sample, because 3d0 Ti4 + has no valence electrons, the magnetic behavior of the Yb3 + sublattice is isolated from any interference magnetic interaction originating from the B sublattice.
Multi-rare earth materials, namely rare earth functional materials composed of 4 or more elements, are a very complicated system. Therefore, in the process of looking for new rare earth functional materials, according to the characteristics of rare earth ions, based on the phase diagram, a suitable preparation method is found to synthesize rare earth compounds with superior performance. For example, the Gd2MgTiO6 material doped with Eu3 + takes advantage of the high excitation efficiency of the Ti-O charge transfer band and the doping of the second rare earth ions, and there is a weak magnetic even-pole transition in its emission spectrum (5150-7f1, 590 nm) peak and a strong electric dipole transition (5D0-7F2,616 nm) peak, red (616 nm) and orange (590 nm) when mass fraction is doped by 15% Eu the ratio of the maximum . Crystalline alkali and rare earth polyphosphate rblap44012: Ln3 + is widely transparent and has the characteristics of high density in the ultraviolet region and rapid emission of rare earth ions in the matrix, which can be used as a candidate material of scintillator, and due to the low concentration quenching of the luminescence of active Ln3 + ions at high concentrations, they are also widely studied for other optical applications . In the zirconia oxide system, with the increase of rare earth ion radius, the total conductivity decreases, and the conductivity of BaZr1-xYxO3-δ material increases with the increase of yttrium concentration . In the phosphate system, with the increase of the number of rare earth atoms, the coordination number of RE3 + has a downward trend, and the RE-O distance between atoms regenerates the contraction of lanthanum elements. Therefore, the current rare earth environment depends on the ion size; Rare earth accumulates in glass with 7 coordination RE3 + environment, in which the composition is close to the limit of metaphosphate .
Relationship between rare earth ions and functional properties
Rare earth elements are active metals between alkali metals and transition metals. Rare earth elements are allowed to lose different numbers of electrons from their s, d and f subshells. For RE element, the external electronic domain can be represented as 4f0~145d0~16 s2. Due to valence electrons, these outer electrons located outside the nucleus can be transferred when the atoms react together. Generally speaking, the outer electron is the only electron involved in binding. Generally, there are several possible orbital types in the bonding atomic orbital, namely, sp hybridization, sp hybridization and sp df hybridization . Chemical bonds between rare earth elements and ligands determine the local symmetry and crystal structure of materials.
The change of valence state is an important factor of the functional characteristics of initiation, adjustment and conversion. Because the rare earth outer valence electrons and valence state orbits are more than other elements, there are different chemical bond modes and coordination configurations, designing a reasonable coordinated environment with Ln cation as the center has become the key strategy for manufacturing new Ln-based advanced materials . Therefore, mastering the orbital hybridization model, exploring the coordination number of rare earth ions, coordination structure and the mechanism of outer orbital hybridization will provide necessary basis for discovering new rare earth functional materials and improving their functional characteristics. As shown in fig. 7, the role of rare earth ions in new functional materials.
Figure 7. The role of rare earth ions
Conclusions and prospects
Starting from the characteristics of rare earth ions, this paper systematically summarizes the research progress of rare earth ions in the composition and application of rare earth functional materials in recent years. Rare earth ions have stable physical and chemical properties, unique optics, magnetic, electrical and other properties make the rare earth functional materials become one of the important basic strategic materials in the field of advanced technology such as superconductivity, strong light lighting, optical refrigeration, magnetic refrigeration and so on. Therefore, the exploration of new rare earth functional materials, in addition to relying on the search and synthesis of matrix materials, must also carry out in-depth research on the mechanism between rare earth ions and the structure and physical properties of materials and the essence of rare earth ions. Explore chemical bonds between rare earth elements and ligands, optimize the local structure of rare earth materials, so as to improve the properties of rare earth functional materials. Finding new functional rare earth materials requires the cooperation of experts in the fields of physics, chemistry, materials science, crystallography and so on, only in this way can the comprehensive and lasting development of rare earth crystallography be guaranteed, and basic research in related fields be promoted and original achievements of world leading level be obtained.
Author: HU J iale, XUE Dongfeng. Research Progress on the Characteristics of Rare Earth Ions and Rare Earth Functional Materials[ J ]. Chinese J ournal of Applied Chemistry, 2020, 37(3): 245-255. doi: 10.11944/ j. Invest-0518.2020.03.190350
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