207 results about "Sodium niobate" patented technology

The invention discloses a potassium-sodium niobate based oxide up-conversion luminescent material with a chemical formula of (Na0.5+sigmaK0.5-yAy)1-x-zMxYbzNbO3:Phi C or (Na0.5-yAyK0.5+sigma)1-x-zMxYbzNbO3: Ph iC, wherein M is selected from one or more of Li, Na, K, Tl and Ag; C is selected from one or more of Li, Na, K, Tl and Ag; A is one or more of K, Na and Li; a value range of x is not smaller than 0.00001 and not bigger than 0.15, the value range of y is not smaller than 0 and not bigger than 0.5, the value range of z is not smaller than 0 and not bigger than 0.35, the value range of sigma is not smaller than 0 and not bigger than 0.1 and the value range of Phi is not smaller than 0 and not bigger than 0.1. The luminescent material disclosed by the invention further has up-conversion luminescent characteristic in addition to piezoelectric performances, ferroelectric performances and dielectric performances, belongs to photoelectric multifunctional materials, and not only can be applied to the piezoelectric field, but also can be applied to the sensor field, the information storage field, the biological detection field and the biomedical field.

The invention relates to a thermal stable sodium niobate-based lead-free piezoelectric ceramic and a preparation method thereof. The composition is shown as a general formula of (1-z)[(1-x-y)NaNbO3+xMI+yABO3]+zMII; in addition, the x is greater than 0.08 but smaller than 0.15; the y is greater than 0 but smaller than 0.1; the z is greater than 0 but smaller than 0.1; the MII is one or several kinds of metal oxides. The thermal stable sodium niobate-based lead-free piezoelectric ceramic belongs to the field of a functional ceramic material. The ceramic can be obtained by using a conventional piezoelectric ceramic preparation technology and by using industrial raw materials; the prepared sodium niobate-based lead-free piezoelectric ceramic composition has good piezoelectric performance, goodtemperature stability and good process stability, can realize the replacement on partial conventional lead-containing piezoelectric ceramic, and has the practicability.

The invention provides a method for comprehensive recovery of tantalum and niobium from red mud. The method comprises the following steps: mixing red mud with a reducing agent to carry out reducing roasting, and then carrying out magnetic separating to obtain magnetic iron ore concentrate and non-magnetic slag; fusing the non-magnetic slag and a mixture of sodium hydroxide and sodium carbonate at 500-800 DEG C to transform tantalum and niobium into sodium tantalum oxide and sodium niobate; crushing the molten massive melt, and heating, agitating and leaching by using a certain amount of acid, so that main ingredients of the non-magnetic slag, such as calcium, aluminum, silicon and a little of oxide of iron are dissolved, and the complicated compounds of tantalum and niobium are also decomposed to be transformed into hydroxide, but still reserved in the slag to be gathered; heating and dissolving the acid-leaching slag in a mixed acid of HF and HNO3; adding water and H2SO4 to dilute after cooling; carrying out tantalum and niobium separation and extraction on the diluted solution by adopting a liquid-film method. By adopting the method, not only can tantalum and niobium in the red mud be gathered, but also separate recovery and extraction of tantalum and niobium can be achieved.

The invention discloses a niobate-series leadless piezoelectric ceramic-polymer three-phase composite material with a high dielectric constant and a preparation method thereof. The method comprises the following steps of: burdening according to a formula, i.e., (1-x)(LiaNabK1-a-b)(Nb1-cSbc)O3-xABO3-yM and preparing sodium niobate kalium-based leadless piezoelectric ceramic powder by adopting the conventional solid phase method; and mixing ceramic powder, a polymer and a multiwall carbon nanotube into composite material powder according to a designed proportion, adding an organic solvent for dissolving the polymer, performing ultrasonic dispersion, adding ethanol for precipitating the polymer, filtering, performing cold press molding on the composite material powder, heating, and sputtering a gold electrode on the surface of the molded composite material powder to obtain a niobate-series leadless piezoelectric ceramic-polymer-multiwall carbon nanotube three-phase composite material with a high dielectric constant. The relative dielectric constant of the composite material can be up to 105-108 at 1kHz, and the three-phase composite material has a good application prospect.

The invention discloses a piezoelectric material for lead-free piezoelectric ceramic with potassium-sodium niobate and a preparing method, which strengthens the ferroelectric performance of potassium-sodium niobate ceramic and further improves the piezoelectric performance. The material of the invention comprises anhydrous potassium carbonate, natrium carbonicum calcinatum, niobium pentaoxide and dibismuth trioxide, the stoichiometric proportion of the lead-free piezoelectric ceramic is (K0.5 Na0.5) Nb3 + x weight percent Bi 2O3, wherein the x is more than or equal to 0 and less than or equal to 1, the piezoelectric material for lead-free piezoelectric ceramic with potassium-sodium niobate is obtained through mixture making, drying and burnishing, granulation, molding, sintering and after polarization by a silver electrode; therefore, the densification of the ceramic is improved, polarized drain current of the ceramic is reduced, and the polarization process is carried out more easily; moreover, the piezoelectric material adopts the material from a conventional process and industry, has the characteristics of good process stability and no pollution.

The invention discloses a method for preparing sodium niobate powder. The method comprises: taking Nb2O5 and NaOH as raw materials and KOH as mineralizer or taking Nb2O5 as raw materials and NaOH as mineralizer; weighing 20 to 40 percent of NaOH ,55 to 75 percent of deionized water ,1 to 3 percent of Nb2O5 and 2 to 4 percent of KOH by weight when Nb2O5 and NaOH are taken as the raw materials and KOH is taken as the mineralizer; weighing 20 to 40 percent of NaOH ,55 to 75 percent of distilled water and 1 to 3 percent of Nb2O5 by weight when Nb2O5 is taken as the raw materials and NaOH is taken as the mineralizer; adding the weighed raw materials to a beaker respectively; stirring with a glass rod to completely dissolve the raw materials; and obtaining the sodium niobate powder through heating, cooling, cleaning and drying processes. The powder prepared by the method for preparing sodium niobate powder is pure orthorhombic sodium niobate powder. Moreover, as the method adopts a microwave internal heating mode, the method has the advantages of heating more uniformly, raising heating rate and greatly shortening reaction time, along with simple process control, strong repeatability, short process cycle and energy conservation.

The invention relates to a microwave hydrothermal synthesis method for preparation of sodium-potassium and niobate-potassium lead-free piezoelectric ceramic powder, which belongs to the functional material field. The invention is characterized in that: NaOH or KOH solution and Nb2O5 are used as reactants; NaNbO3 or KNbO3 ceramic powder is synthesized by microwave hydrothermal technology; the concentration of NaOH or KOH is 4-8mol/L while the input amount of the Nb2O5 is 0.01 to 0.02 mol; and the reaction temperature is 110 to 150 DEG C and the heat is preserved for 2 to 6 hours. The microwave hydrothermal synthesis method for preparation of sodium-potassium and niobate-potassium lead-free piezoelectric ceramic powder combines the unique heating features of a microwave and the advantage of the hydrothermal method, thus having simple technique, low cost, low consumption and very wide application prospect.

The invention relates to a preparation method of flaky sodium niobate microcrystalline powder; first, sodium carbonate, niobium oxide, bismuth oxide and sodium chloride serve as preparation raw materials, and flaky bismuth sodium niobate with excellent asymmetric shape is synthesized; and then flaky bismuth sodium niobate, sodium carbonate and sodium chloride serve as preparation raw materials, and the flaky sodium niobate microcrystalline powder is synthesized through a molten salt method, wherein the ratio of the total weight of the sodium carbonate and the flaky bismuth sodium niobate to the weight of the sodium chloride is 2:1; and the sodium carbonate is fully excessive, and the molar ratio of the sodium carbonate to the flaky bismuth sodium niobate is 1.0 to 1.25:1. The flaky sodium niobate microcrystalline powder prepared by the invention does not cohere and has good dispersion, the width and thickness uniformity of the microcrystalline powder is good, the asymmetric shape is good and the crystalline phase is single. The preparation method of the flaky sodium niobate microcrystalline powder is characterized by simple preparation process, little pollution, small formula error, low cost, easy control of the process, good repeatability and stability of the product, and easy realization of industrial production.

The invention discloses a high-piezoelectric property and high-stability anti-reduction potassium-sodium niobate-based leadless piezoelectric ceramic and a preparation method thereof. The chemical formula of the piezoelectric ceramic is as follows: (1-x)[(1-y)K0.5Na0.5Nb<1-z>Ta<z>O<3-y>Bi0.5(Na0.82K0.18)0.5ZrO3]-xCaZrO<3+k%>M, wherein x, y, z and k represent molar fractions, x is greater than or equal to 0 and less than or equal to 0.03, y is greater than or equal to 0.02 and less than or equal to 0.05, z is greater than or equal to 0 and less than or equal to 0.12, k is greater than or equalto 0.2 and less than or equal to 0.6, x, y and z are not zero at the same time, and m represents a manganese compound. According to the anti-reduction potassium-sodium niobate-based leadless piezoelectric ceramic provided by the invention, the piezoelectric constant d33 reaches 275 pC/N or above, the planar electromechanical coupling coefficient kp can reach 0.50, the ceramic strain can reach 0.20% in a 50 kV/cm electric field, and the maximum inverse piezoelectric constant d33* reaches 500 pm/V (E = 25 kV/cm). Under a 35kV/cm electric field, the d33* of a sample at room temperature is equal to 460pm/V, and the temperature Te of the inverse piezoelectric coefficient d33* is stabilized within 125 DEG C within the fluctuation range of +/-10%.

A sodium niobate powder includes sodium niobate particles having a shape of a cuboid and having a side average length of 0.1 μm or more and 100 μm or less, wherein at least one face of each of the sodium niobate particles is a (100) plane in the pseudocubic notation and a moisture content of the sodium niobate powder is 0.15 mass % or less. A method for producing a ceramic using the sodium niobate powder is provided. A method for producing a sodium niobate powder includes a step of holding an aqueous alkali dispersion liquid containing a niobium component and a sodium component at a pressure exceeding 0.1 MPa, a step of isolating a solid matter from the aqueous dispersion liquid after the holding, and a step of heat treating the solid matter at 500° C. to 700° C.

The invention discloses a novel high-energy-storage and high-efficiency sodium niobate-based ceramic material of which the composition formula is (1x)[0.9 NaNbO3-0.1Bi(Mg2/3Ta1/3)O3]x(Bi0.5Na0.5)0.7Sr0.3TiO3, x is the molar percentage, and x is more than or equal to 0 and less than or equal to 0.40. The invention also discloses a preparation method of the sodium niobate-based ceramic material, which includes the novel high-energy storage and high-efficiency sodium niobate-based ceramic material, and further comprises the following steps: preparing sodium niobate-based ceramic powder; putting the sodium niobate-based ceramic powder into a ball milling tank for predetermined treatment, and pressing a product into a green body for presintering; pouring a product into the ball-milling tank after pre-sintering is completed, carrying out predetermined treatment again, and pressing the powder into a wafer by using a mold after pre-sintering is completed; sintering the wafer in a muffle furnace according to sintering conditions to prepare the sodium niobate-based ceramic material, and introducing strong ferroelectric Bi(Mg2/3Ta1/3)O3 and (Bi0.5Na0.5)0.7 Sr0.3TiO3 to form a uniform solid solution with NaNbO3 antiferroelectric so that the maximum polarization strength and breakdown field strength of the ceramic material are improved, wherein the energy storage density of the dielectric ceramic material is improved.

The invention relates to Na<+> compensatory potassium-sodium niobate lithium base leadless piezoelectric ceramics and a low-temperature sintering method thereof, which belongs to the filed of functional ceramic materials. The general formula of chemical composition can be represented as (Naa+xKbLic)NbO3; wherein, a, b, and c represent the molar fraction of the components such as Na, K, Li respectively; and a plus b plus c equals to 1; x represent the molar fraction of the compensatory Na<+>; the value range of each parameter is that: a is more than 0.20 and less than 0.80, b is more than 0.20 and less than 0.80, c is more than 0.00 and less than 0.30, and x is more than 0.00 and equal or less than 0.20. The preparation method of the ceramics system comprises the processing steps of mixing raw materials, baking, molding, sintering, baking sliver and polarization, etc. The Na<+> compensatory potassium-sodium niobate lithium base leadless piezoelectric ceramics and the low-temperature sintering method of the invention have the advantages of effectively reducing the baking temperature of potassium-sodium niobate lithium base leadless piezoelectric ceramics by the compensation of Na<+> and preparing leadless piezoelectric ceramics with good property material at the low temperature of 800 to 1000 DEG C.

The invention provides a preparation method for a sodium columbate ceramic material with stable antiferroelectricity and low dielectric loss, belonging to the field of dielectric ceramic materials. With the method, stability of an antiferroelectric phase in pure sodium columbate ceramic is realized; ferroelectric phase induced by an electric field does not occure in a 100 kv/cm high electric field; and the material has low dielectric loss (less than 2%). The preparation method comprises the following steps: weighing Na2CO3 and Nb2O5 according to a mol stoichiometric ratio of Na to Nb of 1: 1 and putting the two raw materials into a ball milling tank for ball milling, with absolute ethyl alcohol as a ball milling medium; and subjecting powder obtained after batch mixing to dry grinding through a high-energy ball milling method so as to obtain nanometer sodium columbate powder, directly pressurizing and molding the obtained nanometer powder without addition of any binder and then carrying out sintering at 1350 to 1375 DEG C so as to obtain a ceramic body. Determination of a stable antiferroelectric phase is realized through electric performance testing. The preparation method provided by the invention is simple and has low energy consumption. The prepared sodium columbate ceramic material has stable antiferroelectricity and low dielectric loss.

A composite piezoelectric ceramic includes a compact of crystal particles including at least one of potassium niobate (KNbO₃) and sodium niobate (NaNbO₃) and optionally further including lithium niobate (LiNbO₃), and a layer containing barium titanate (BaTiO₃) that is disposed on the surface of the compact while forming a heterojunction with the compact. A piezoelectric device includes the composite piezoelectric ceramic.

The invention relates to a novel sodium niobate/bismuth titanate lithium system leadless piezoelectric ceramic composition containing perovskite antiferroelectric NaNbO3 and ABO3 compound Bi0.5Li0.5TiO3 with a general formula expressed as (1-x)NaNbO3-xBi0.5Li0.5TiO3, wherein x is great than or equal to 0.025 and less than or equal to 0.25. The leadless piezoelectric ceramic composition can also contain one or more oxides with a general formula of (1-x)NaNbO3-xBi0.5Li0.5TiO3((100-a) mol%)+MalphaObeta (a mol%), wherein MalphaObeta is one or more oxides, the molar ratio of the content a of MalphaObeta to the main component (1-x)NaNbO3-xBi0.5Li0.5TiO3 is 0-3%, M is an element with (+1)-(-6) valence and can be combined with oxygen to form a solid oxide, and alpha and beta are used for respectively expressing the atom numbers of the corresponding element M and oxygen in the related oxide. The system leadless piezoelectric ceramic composition obtained by adopting traditional piezoelectric ceramic preparing technology is characterized in that the optimal value d33 can be up to more than 50pC/N and the kp can be up to more than 15%, and has the advantages of high Curie temperature, good heat stability, good compactness and stable process.

A piezoelectric element exhibiting a small leakage current density and high reliability as compared with a KNN thin film piezoelectric element in the related art is provided. The piezoelectric element is characterized by including a lower electrode, a piezoelectric layer primarily made from potassium-sodium niobate, which is a perovskite type compound represented by a general formula ABO₃, and an upper electrode, wherein the piezoelectric layer is present between the lower electrode and the upper electrode, and the piezoelectric layer has the value determined by dividing the maximum value of intensity of a diffraction peak, where the angle of 2θ is within the range of 21.1°≦2θ≦23.4° in the X-ray diffraction pattern (2θ/θ), by the intensity of a diffraction peak, where 2θ is within the range of 30.1°≦2θ≦33.3°, of 0.04 or less.

The invention relates to the field of preparation and application of nanowire photocatalytic materials, in particular to a method for preparing a catalyst for photocatalytic CO2 reduction. The method comprises the following steps of: synthesizing a precursor, namely Na2Nb2O6.H2O nanowires by a surfactant-assisted hydrothermal method, and calcining in an electric furnace in air atmosphere to prepare sodium niobate nanowires. The generation rate of CH4 converted from CO2 by the sodium niobate nanowires is improved by 20 times compared with that of the CH4 converted from the CO2 by sodium niobate prepared by a high-temperature solid-phase reaction method.

The invention belongs to the technical field of preparation methods of piezoelectric ceramic materials, and particularly relates to a preparation method of multi-element doped potassium-sodium niobate-based lead-free piezoelectric ceramic. The chemical formula of the multi-element doped potassium-sodium niobate-based piezoelectric ceramic is (Na < 0.52 > K < 0.48 >) Nb < 1-x > Ta<x>O < 3-y > BaZrO < 3-z > MnCO<3>. The preparation method comprises the following steps: weighing raw materials to prepare a green body, carrying out glue removal treatment, heating to 1100-1250 DEG C, and sintering in a reducing atmosphere (consisting of nitrogen with the volume fraction of 99-95% and hydrogen with the volume fraction of 5-1% for 1-3 hours. The inverse piezoelectric coefficient of the multi-element doped potassium-sodium niobate-based lead-free piezoelectric ceramic prepared in the reducing atmosphere under an electric field of 4kV/mm is 280-400pm/V, the piezoelectric constant d33 is 180-250pC/N, the planar electromechanical coupling coefficient kp is equal to 20-25.3%, and the dielectric loss tan delta is not higher than 0.03.