Potassium niobates

Simple ABO compounds in addition to BaTiO are cadmium titanate [12014-14-17, CdTiO lead titanate [12060-00-3] PbTiO potassium niobate [12030-85-2] KNbO sodium niobate [12034-09-2], NaNbO silver niobate [12309-96-5], AgNbO potassium iodate [7758-05-6], KIO bismuth ferrate [12010-42-3], BiFeO sodium tantalate, NaTaO and lead zirconate [12060-01 -4], PbZrO. The perovskite stmcture is also tolerant of a very wide range of multiple cation substitution on both A and B sites. Thus many more complex compounds have been found (16,17), eg, (K 2 i/2) 3 ... 

Sodium niobate(7 6) [12201 -59-17, 7Na20 6Nb20 3IH2O or Naj4Nbj2 037-31H2 0, forms a crystalline precipitate when a hot solution of a soluble niobium compound is added to a hot concentrated sodium hydroxide solution. It is insoluble in the presence of excess sodium hydroxide but is sparingly soluble in pure water. It also can be formed by addition of sodium hydroxide or chloride to a solution of the 4 3 potassium niobate. 

Potassium iodide, 20 634 Potassium ions, 20 597, 598, 641 in soap-water system, 22 727 Potassium isotopes, 20 598 Potassium magnesium sulfate, 20 626 Potassium manganate(V), 15 592 Potassium manganate(VI), 15 594-596 Potassium metal, 20 604 production of, 20 600 reducing power of, 20 599 Potassium muds, 9 4 Potassium niobate, 17 152-153 Potassium nitrate, 20 609, 634-636 solubility of, 20 636t uses of, 20 636... 

Bulk potassium niobate (KNbOs) is well suited to our needs, beeause birefringent type-I non-critical phasematehing (NCPM) can be exploited for highly efficient SHG of 850 nm at room temperature . This NCPM avoids any spatial waUc-off between the fundamental and second harmonic beams, as well as maximizing the angular acceptance of the phasematching process. 

L.E. Busse, L. Goldberg, M.R. Surette, and G. Mizell, Absorption Losses in MgO-doped and undoped potassium niobate, JoMfno/ of Applied Physics 75(2), 1102-1110 (1994). 

The monoxide has been variously described, according to the method of preparation, as a black powder, or glistening crystals, or beautiful black cubes. Its density varies from 6 3 to 6-7, and it is a good conductor of electricity. On being heated in air it oxidises readily to the pentoxide with considerable evolution of heat. It dissolves in hydrofluoric acid and hydrochloric acid with evolution of hydrogen, and a pentavalent niobium salt is formed in solution. It is also dissolved by boiling potassium hydroxide to form potassium niobate. This behaviour of niobium monoxide towards acids and alkali indicates that divalent salts of niobium are too unstable to exist. A divalent chloride of tantalum has, however, recently been isolated (see p. 192). 

The alkali niobates are most conveniently prepared by the action of caustic alkalis on niobic acid or on solutions of niobium oxytri-fluoride. Other compounds of niobic acid and bases are generally prepared by fusing niobic add with the oxide, hydroxide, carbonate, or other salt of the metal. Occasionally double decomposition of a soluble alkali niobate and a soluble salt of the metal has been employed. Larsson s method1 consists in predpitating a solution of potassium niobate with a salt of a metal the dried predpitate is fused for thirty-six hours at a high temperature with boric acid, and the melt is boiled with water to which hydrochloric acid has been added. The residue consists of crystals of the insoluble niobate of the metal, usually the metaniobate. 

Niobates are usually insoluble in water even many of the alkali niobates are insoluble. Insoluble alkali niobates are formed when niobium pentoxide is fused with only small proportions of alkali carbonate. 7 6 Sodium niobate, 7Na20.6Nb205. H20, is insoluble in solutions of high sodium-ion concentration, and is therefore precipitated. by the addition of sodium salts to solutions of potassium niobate. Ammonium niobates are unknown when excess of an ammonium salt is added to a solution of an alkali niobate, a voluminous precipitate is thrown down which is rapidly decomposed by water to yield niobic 1 Larsson, Zeitsck. anorg. Ch m., 1896,12,197. 

Cadmium Metaniobate.—The anhydrous salt, Cd0.Nb205, is obtained by fusing potassium niobate with cadmium chloride. It forms yellowish-brown, glistening crystals, the density of which is 5-93.4 The hydrated salt Cd0.Nb20s.3 H20 is thrown down as a pale yellow precipitate on adding a solution of a cadmium salt to sodium metaniobate.8... 

Calcium Pyroniobate, 2Ca0.Nb205, is prepared by fusing with calcium chloride either niobium pentoxide or the precipitate obtained by the action of calcium chloride on potassium niobate solution the melt is extracted with water containing hydrochloric add,10 when the salt remains in small, colourless, glistening, prismatic crystals.11 Density at 17° C. 4-484. 

Lithium Niobate, 7Li2O.6Nb2O6.20H2O, is a crystalline substance which results from the action of lithium nitrate on a concentrated solution of potassium niobate, K20.3Nb205.5H20.8... 

Another manganese niobate, 3Mn0.5Nb205, has been obtained by adding manganese sulphate to potassium niobate and fusing the precipitate with boric acid. It consists of small, greyish-yellow, prismatic rods, density 4-97.1... 

Potassium Niobates are generally produced by fusion of the metal or the pentoxide with potassium hydroxide, potassium carbonate, or potassium nitrate,3 or by the action of solutions of caustic potash or of potassium carbonate on niobic acid.4 They are among the most stable of the niobates their solutions can be boiled without precipitation of the acid. On being treated with sodium salts, for example sodium chloride, sodium niobates are precipitated. 

Potassium niobate, K 20.2Nb 2Os. 5JH 20, remains undissolved in the crystalline residue left after fusing equimolecular proportions of niobic acid and potassium carbonate and extracting the melt with water. ... 

Potassium niobate, 8K20.7Nb20B.82H2Q, predpitates out on slow evaporation of solutions of either the 4 3 salt or the 7 6 salt. It forms rhombic bipyramids which can be recrystallised unchanged a b c=0 9584 1 0 7083. Twenty-three molecules of water are lost at 100° C. It readily yields supersaturated solutions. When its aqueous solutions are treated with a current of carbon dioxide they predpitate salts which contain a larger proportion of niobic add.9... 

Potassium niobate, 7K20.6Nb208.27H20, is predpitated by the addition of alcohol to an aqueous solution of the 4 3 salt. The product is redissolved in water and reprecipitated several times.19... 

Potassium niobate, 8Ks0.2Nb20B.13H20, is obtained in rhombic crystals by adding excess of potassium hydroxide to a solution of the 4 3 salt and evaporating slowly. It effloresces rapidly in the air and loses seven molecules of water of crystallisation at 100° C.a... 

Potassium niobate or potassium pyroniobate, 2K20.Nb20B. 11H20, is an insoluble powder which is obtained by fusing the 1 2 salt with excess of potassium carbonate and extracting the product with water.3... 

Potassium niobate and 3 1 potassium niobate (the ortho-salt) have also been reported.4... 

Thorium Niobate, 5Th02.16Nb205, is prepared by adding thorium sulphate to a solution of potassium niobate, fusing the precipitate with borax and boiling the melt with water containing hydrochloric acid. It forms doubly refracting, prismatic needles density 5-21.7... 

Potassium Pemiobate, K3Nb08s is prepared by the action of caustic potash and 3 per cent, hydrogen peroxide on 4 3 potassium niobate. It yields tetragonal crystals. 

There are two principal types of materials that can function as piezoelectrics the ceramics and polymers. The piezoelectric materials most widely used are the piezoceramics based on the lead zirconate titanate, PZT, formations, mixed sodium and potassium niobates, lithium niobate, and quartz. The advantages of these piezoceramics are that they have a high piezoelectric activity and they can be fabricated in many different shapes. 

Petrov V, Noack F. Mid-infrared femtosecond optical parametric amplification in potassium niobate. Opt Lett 1996 19 1576-1578. 

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