Synthesis and X—ray Powder Diffraction Characterization of A New Niobate Crystal Ba4Na2VNb9O30

A new niobate crystal Ba4Na2VNb9O30 was synthesized in BaO-Na2O-V2O5-Nb2O5 system for the first time.Its shape, optical properties ,melting point and chemical stability were studied.X-ray powder diffraction study determined that this compound assumes a tetragonal tungsten bronze structure with space group P4bm(100) and lattice parameters a=b=12.4275(2), c=3.970(3). The new compound may be one kin of photorefractive srystals.     

Synthesis and Characteristic of a New Niobate: Ba_5NaCr_(0.5)Nb_(9.5)_O_(30)

1　IntroductionTungsten bronze type (TTB)neonatematerialshavereceivedconsiderableattentionbecauseoftheirdielectricandferroelectricpropertiesandeaseofpreparation[1 5] .Thebronzecompositionscanberepresentedbythegeneralformulasas (A1 ) 4 (A2 ) 2 C4B1 0 O3 0…     

钽酸盐Ba5LaZnTa9O30的结构及其介电特性

在BaO-ZnO-Ta2O5体系中通过掺La3+合成了钽酸盐Ba5LaZnTa9O30采用粉晶X射线衍射(XRD)对其结构进行了分析,并测试了其陶瓷体的介电特性.结果表明,Ba5LaZnTa9O30在室温下属于填满型四方钨青铜结构顺电相,晶胞参数为a=1.259 09(4)nm,c=0.396 22(2)nm,α=β=y=90°;频率为1 MHz时Ba5LaZnTa9O30陶瓷的室温相对介电常数为89;而且介电损耗仅为0.006 7.     

新铌酸盐A5NdSn3Nb7O30的合成与介电特性

通过固相反应法在AO-Nd2O3-SnO2-Nb2O5(A=Ba,Sr)体系中合成了填满型钨青铜结构新铌酸盐A5NdSn3Nb7O30。分别采用X射线衍射分析和扫描电镜进行了结构分析,并进行了介电性能测试。结果表明,它们室温时都为四方钨青铜结构顺电相。A5NdSn3Nb7O30(A=Ba,Sr)陶瓷体具有高的室温相对介电常数,1 MHz时分别为182与144;低的介电损耗,分别为1.8×10-3和6.2×10-4;其介电常数温度系数(τε)分别为-1 071×10-6K-1和-507×10-6K-1。     

Synthesis and Characteristic of a New Niobate:Ba_5NaCo_0.5Nb_9.5O_30

A new niobate crystal was synthesized for the first time in BaO-Na2O-Co2O3 -Nb2O5 system by solid state reaction and the flux method. The new compound was studied by X-ray diffraction, electron probe. N-ray microanalysis, chemical analysis and SEM. The result of the X-ray diffraction shows that Ba5 NaCo0.5 Nb9.5 OK) belongs to tetragonal tungsten bronze structure with space group P4bm( 100) and lattice parameters a = b = 12.4453(2) A, c = 3. 9770 (3) A and Z = 1. The structure of the compound is different from that of Ba4Na2Nb10O30     

新铌酸盐A5LaSn3Nb7O30(A=Ba,Sr)的结构与介电特性

通过固相反应法,在AO-La2O3-SnO2-Nb2O5(A=Ba,Sr)体系合成了填满型钨青铜结构新铌酸盐Ba5LaSn3Nb7O30与Sr5LaSn3Nb7O30。采用X射线衍射分析和扫描电镜进行了结构分析,并测试了其介电性能。结果表明:Ba5LaSn3Nb7O30与Sr5LaSn3Nb7O30室温时均为四方钨青铜结构顺电相,其陶瓷体都具有高的介电常数、低的介电损耗与较小的介电常数温度系数。频率为1 MHz时,Ba5LaSn3Nb7O30陶瓷体的室温相对介电常数为171,介电损耗约为1.2×10-3;Sr5LaSn3Nb7O30陶瓷体的室温相对介电常数为164,介电损耗约为5.4×10-4。     

SYNTHESIS OF NEW BIOBATE CRYSTAL Ba2.6Na0.4Cu0.2Nb4.8O15

New niobate crystal Ba_(2.6)Na_(0.4)Cu_(0.2)Nb_(4.8) O_(15) was synthesized in BaO-Na_2O-CuO-Nb_2O_5 system. Its morphology, optical properties, melting point and chemical stability were studied. X-ray power diffraction study determined that this compound is orthorhombic tungsten bronze structure with space group Cmm~2 and lattice parameters a=17.692(2),b=17. 684(2),c=3.998(2). The new compound may be one kind of photorefractive crystals.     

STRUCTURAL AND FERROELECTRIC PROPERTIES OF A NEW NIOBATE : Sr6FeNb9O30

A new niobate Sr_6FeNb_9O_(30) was synthesized in the ternary system SrO-Fe_2O_3-Nb_2O_5 for the first time. The crystal structure was determined by X-ray diffraction and dielectric measurement, and it belongs to orthorhombic tungsten bronze structure at room temperature with unit cell parameters a=1.7554(1) nm, b=1.7534 (1) nm, c=0.77870 (6) nm. Dielectric constants measurement show that Sr_6FeNb_9O_(30) has two phase transitions, paraelectric to ferroelectric at 185C and ferroelectric to ferroelastic at 70C.     

Synthesis and Dielectric Properties of New Niobate Ba_5BiTi_3Nb_7O_(30)

1　ＩｎｔｒｏｄｕｃｔｉｏｎＦｅｒｒｏｅｌｅｃｔｒｉｃｓｗｉｔｈｔｈｅｔｅｔｒａｇｏｎａｌｔｕｎｇｓｔｅｎｂｒｏｎｚｅｓｔｒｕｃｔｕｒｅａｒｅｔｈｅｉｎｔｅｒｅｓｔｉｎｇｃｏｍｐｏｕｎｄｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｈｉｇｈｅｌｅｃｔｒｏ ｏｐｔｉｃ ,ｐｉｅｚｏｅｌｅｃｔｒｉｃ ,ｎｏｎｌｉｎｅａｒｏｐｔｉｃａｌｅｆｆｉｃｉｅｎ ｃｉｅｓａｎｄｉｔｓｉｎｔｅｒｅｓｔｉｎｇｆｅａｔｕｒｅｓｆｒｏｍｔｈｅｖｉｅｗｐｏｉｎｔｏｆｐｈａｓｅｔｒａｎｓｉｔｉｏｎｓ[1- 3] .Ｔｕｎｇｓｔｅｎｂｒｏｎｚｅｓｔｒｕｃ…     

Preparation, Characterization and Dielectric Properties of Ba6Mg0.67Nb9.33O30 Ceramic

A new niobate Ba6Mg0.67Nb9.33O30 was ssnthesized in the BaO-MgO-Nb2O5 system by solid state reaction at 1350 ℃ for 48 b. The strncture and dielectric properties of Ba6Mg0.67Nb9.33O30 were determined by X-ray pouder diffraction, straining electron microscopy and dielectric measurements. The results show that Ba6Mg0.67Nb9.33O30 belongs to ferroelectric phase of filled tetragonal tungsten bronze structure at room temperature with unit cell parameters ： a = 1. 26052（4） nm , c = 0.40045（2） nm, space group P4bm , calculated density 5 . 707g. cm ^-3 . Ba6Mg0.67Nb9.33O30 belongs to relaxor ,ferroetectrics undergoing diffusive phase transition, and the transition temperature （ Tc ） is 30 ℃ observed at 10 kHz. At room temperature, Ba6Mg0.67Nb9.33O30 eeramic has a high dielectric constant 850 at 1 MHz and a low dielectric loss of 0. 0052.     

Preparation, Characterization and Dielectric Property of Sr_5LaTi_3Nb_7O_(30) Ceramic

1　IntroductionElectronicmaterialswithhighdielectricconstant,highQ valuesandgoodstabilityoftemperaturecoefficientofresonantfrequencyandlowdielectriclosshavebeenextensivelystudiedbecauseoftheirapplicationsindis creteandmultiplayer (MLC)capacitors ,microwav…     

掺杂对一些钨青铜铌酸盐晶体结构及性能影响

研究了掺杂对钨青铜（TB）型铌酸盐晶体的结构、生长及性能的影响。使用X射线衍射技术研究了掺铬铌酸锶钡晶体的晶格常数。在TB型铌酸盐晶体的合成中，掺杂实际是晶体分子设计的一部分。TB型铌酸盐晶体中掺杂离子的占位及数量与晶体中阳离子的种类及组成是密切相关的。     

Structural and Dielectric Properties of Ba5RNiNb9O30 （R = La, Nd and Sm） ceramics

1 IntroductionSince the discovery of ferroelectricity and relatedproperties in BaTiO3,a large amount of research work onoxidesin search of novel materials for industrial applica-tions ,has been done .High performance dielectric ceram-ics are applied as key materials for resonators , discreteand multiplayer (MLC) capacitors ,andtemperature com-pensating capacitors . Some ferroelectric oxides are alsovery important due to the rapid progress in microwavetelecommunications ,satellite broadcastin…     

SYNTHESIS AND CRYSTAL STRUCTURE OF A NEW COMPOUND Sr6Sn2Nb8O30

A new compound Sr6Sn2Nb8O30 was found in the ternary system of SrO-SnO2-Nb2O5. The transparent colorless crystal with needle-like shape can be grown by flux method. The crystal structure of new compound was determined by X-ray diffraction, and its belongs to tungsten bronze structure. Sr6Sn2Nb8O30 crystallizes in orthorhombic system with unit cell parameters a= 17. 579 (DA,6= 17. 509(DA,c=7. 7880(5)A,Z = 4 and space group Cmm2.     

盐酸柳叶水甘草碱晶体结构解析

从非洲伏康树籽提取出盐酸柳叶水甘草碱,经纯化、重结晶,获得其多晶粉末。利用其粉末X射线衍射数据,采用直接空间搜索法解析其晶体结构,结果表明：该晶体属单斜晶系,P21空间群,晶胞参数a=1.253 9 nm,b=0.737 1nm,c=1.229 6 nm,α=γ=90°,β=106.192°,Z=2,V=113.649 7 nm3。     

Synthesis and Dielectric Properties of Ba_3NaBiNb_(10)O_(30) Ceramics

1　ＩｎｔｒｏｄｕｃｔｉｏｎＦｅｒｒｏｅｌｅｃｔｒｉｃｓｗｉｔｈｔｈｅｔｕｎｇｓｔｅｎｂｒｏｎｚｅｔｙｐｅｓｔｒｕｃｔｕｒｅｈａｖｅｅｘｃｅｌｌｅｎｔｆｅｒｒｏｅｌｅｃｔｒｉｃ ,ｐｉｅｚｏｅｌｅｃｔｒｉｃ ,ｐｙｒｏｅｌｅｃｔｒｉｃ ,ｅｌｅｃｔｒｏ ｏｐｔｉｃ ,ａｎｄｎｏｎｌｉｎｅａｒｏｐｔｉｃａｌｐｒｏｐｅｒｔｉｅｓ[1,2 ] .Ｔｕｎｇ ｓｔｅｎｂｒｏｎｚｅｓｔｒｕｃｔｕｒｅｃｏｎｓｉｓｔｓｏｆａｎａｓｓｅｍｂｌａｇｅｏｆｃｏｒｎｅｒ ｓｈａｒｅｄ [ＭＯ6 ]ｏｃｔａｈｅｄｒａｌ (Ｍ =Ｔｉ,Ｎｂ ,Ｔａ ,ｏｒ…     

基于粉末X射线衍射的7-ADCA晶体结构解析改进

改进探测器短时间内获得7-ADCA粉末衍射谱图,自动寻峰并运用Dicvol91进行指标化,构建两性离子态分子模型,增加参数精修晶胞,实现7-ADCA多晶衍射结构解析的改进.结果表明:与前期工作相比,晶体的晶系、空间群和晶胞参数基本不变,但原子空间坐标变化显著,Rwp值由14.95%降到7.78%,得到更为准确的晶体结构模型.该模型可以合理解释7-ADCA晶体生长特性.     

新铌酸盐Ba3Nd2Ti2Nb2O15的结构与微波介电特性

采用高温固相反应合成了A5B4O15型五层类钙钛矿结构新铌酸盐Ba3Nd2Ti2Nb2O15. Ba3Nd2Ti2Nb2O15晶体为三方晶系,空间群P3-ml(164),晶胞参数a=5.653 2(1) (A),c=11.611 7 (2) (A),V=321.377 (6)(A)3, Z=1.Ba3Nd2Ti2Nb2O15陶瓷在微波频段具有较高的室温介电常数40.1, 具有较高的Qf值19606GHz,接近于零的谐振频率温度系数 12×10-6K-1,因此,Ba3Nd2Ti2Nb2O15极有可能成为一种新型的介质微波陶瓷材料.     

焦绿石型WO3超细粉体的水热合成与表征

在水热条件下，以钨酸钠为原料，通过调节反应的pH值、酸的量浓度、反应温度及反应时间，找到了制备较佳焦绿石型WO3超细粉体的规律。采用TG，XRD，IR，EPMA等测试手段对样品进行了表征，产物为立方晶系的焦绿石型WO3超微粉体，粒径大小约为24nm。     

铌酸锶铋粉体的水热法制备及表征

以SrCl2·6H2O、Bi（NO2）。·5H2O和Nb2O5为原料,以NaOH为矿化剂,采用水热法在较低温度和较短时间内合成出纯相的SrBi。Nb2O9陶瓷粉体,比传统固相法的合成温度降低了1000℃左右;同时,通过x射线衍射仪（X-raydiffraction,XRD）、扫描式电子显微镜（scanningelectronmicroscope,SEM）等分析手段对粉体的物相、微观形貌进行研究,并分析反应温度、时间和矿化剂浓度对粉体制备结果的影响。结果表明,纯相的SrBizNb2O9粉体合成的最佳工艺条件为240℃,4h,2mol／L,其显微结构较为均匀,平均粒径为1μm,该研究工艺简单,周期较短。