ISSN:
1662-0356
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Natural Sciences in General
,
Technology
Notes:
Ba(Me1/3Nb2/3)O3 (Me=Zn, Co, Ni and Mg) ceramics were prepared using theconventional mixed oxide route; additives included Al2O3, Ga2O3, SiO2, WO3, B2O3 and V2O5.Powders were mixed, milled for 18h, calcined at 1100ºC, remilled pressed into pellets at 100 MPa,sintered in air at temperatures in the range 1350-1550ºC and then cooled at 360C h–1 to 5ºC h–1.Products were characterised in terms of phase analysis (X-ray diffraction), microstructure (SEMand TEM) and electrical properties (relative permittivity, εr, dielectric Q value and temperaturecoefficient of resonant frequency,τf). The Q values of the Ba(Me1/3Nb2/3)O3 ceramics depend on thedegree of cation ordering and the additives. Slow cooling leads to 1:2 ordering of the B sites andenhanced dielectric Q values. For samples cooled at 5ºC h–1 after sintering the Qxf values are in therange 28000 to 98000 GHz, and are in the sequence Ba(Ni1/3Nb2/3)O3, Ba(Co1/3Nb2/3)O3,Ba(Mg1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3. Additions of BaO-4WO3 or V2O5 yield higher Qxf valuesthan Al2O3. Highly ordered Ba(Zn1/3Nb2/3)O3 has a relative permittivity of 39.4, but most otherBa(Me1/3Nb2/3)O3 ceramics exhibit εr of 31-32. The temperature coefficient of resonant frequency,τf, varies from –18 ppm/°C (Ba(Ni1/3Nb2/3)O3) to +32 ppm/°C (Ba(Mg1/3Nb2/3)O3); the sinteringadditives (Al2O3 and BaO-4WO3) change τf by typically 10-16 ppm/°C
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/42/transtech_doi~10.4028%252Fwww.scientific.net%252FAST.45.2323.pdf
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