The influence of Mn doping on the formation and dielectric properties of 0.7BaO·0.3SrO·（1-y）TiO2·yNb2O5 （BSTN） composite ceramics were investigated. The Mn was doped according to the formula 0.7BaO&...The influence of Mn doping on the formation and dielectric properties of 0.7BaO·0.3SrO·（1-y）TiO2·yNb2O5 （BSTN） composite ceramics were investigated. The Mn was doped according to the formula 0.7BaO·0.3SrO·（0.7-z）TiO2·0.3Nb2O5·zMnO2 （BSTNM）. The results show the two phases, perovskite phase BST and the tungsten bronze phase SBN, are coexistence in BSTNM as they are in BSTN composite ceramics. The Mn ions doped in BSTN substitute for Nb5＋ ions in the tungsten bronze phase, and then, the Nb5＋ ions substitute for Ti4＋ ions in the perovskite phase. With the increasing of Mn dopant, the content of the perovskite phase increases while that of the tungsten bronze phase decreases, and the grain size of the perovskite phase decreases. As well as, the phase transition temperature of tungsten bronze phase increases with value z increasing from 0 to about 0.05.展开更多
Composite ceramics of 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 (BSTN) with coexistence of barium strontium titanate, Ba1-xSrxTiO3 (BST), and strontium barium niobate, SrxBa1-xNb2O6 (SBN) phases were successfully ...Composite ceramics of 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 (BSTN) with coexistence of barium strontium titanate, Ba1-xSrxTiO3 (BST), and strontium barium niobate, SrxBa1-xNb2O6 (SBN) phases were successfully prepared in situ by controlling excess components according to a specially designed formula of 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 and by using a traditional ceramic process. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersion spectrometer (EDS) were used to characterize the phase composition, morphology and the micro-area chemical composition of the composite ceramics. The results showed that the SBN tungsten bronze phase appeared and coexisted stably with the BST perovskite phase when the excess content of Nb2O5 was >6mol%, whereas the BST perovskite phase formed and coexisted stably with the SBN tungsten bronze phase when the excess content of TiO2 was >5.3mol%. In the case of the two phases being equivalent to each other in BSTN composite ceramics, Nb2O5 was hard to be resolved into the perovskite phase, however, a few of TiO2 was easy to be resolved in the tungsten bronze phase. The microstructure of the composite ceramics were consisted of two kinds of grains. The smaller polygonal grains were belonged to the BST phase, and the larger ones to the SBN phase. The coexistence of the two phases inhibited the growth of the BST crystal. The density of microstructure of the composite ceramic was higher than that of both the pure BST and SBN calcined at the same temperature for the same time.展开更多
Strontium barium niobate/barium strontium titanate composite ceramics of xSrO·(1-x)BaO·0.5Nb2O5·0.5TiO2 (BSTN in short) with a range of Sr/Ba ratios were fabricated using a modified sol-gel method with ...Strontium barium niobate/barium strontium titanate composite ceramics of xSrO·(1-x)BaO·0.5Nb2O5·0.5TiO2 (BSTN in short) with a range of Sr/Ba ratios were fabricated using a modified sol-gel method with Nb2O5 fine powders suspended in the barium strontium titanate (BST in short) sol solution. Powders obtained from dried gels were calcined at 800 ℃ for 3 h. After preparing bulk ceramics from these powders by sintering at 1200 ℃ for 3 h, the tetragonal tungsten bronze(TTB) phase and perivoskite phase were co-present in compositions between 0.25≤x≤0.75, with the increasing of x value, the peaks of pervoskite phase shift to the high angle position slightly while no changes happened in the peak position of TTB phase. The peak intensity of both two phases were also changed.展开更多
基金Supported by the Research Fund of the Doctoral Program of University of Jinan
文摘The influence of Mn doping on the formation and dielectric properties of 0.7BaO·0.3SrO·（1-y）TiO2·yNb2O5 （BSTN） composite ceramics were investigated. The Mn was doped according to the formula 0.7BaO·0.3SrO·（0.7-z）TiO2·0.3Nb2O5·zMnO2 （BSTNM）. The results show the two phases, perovskite phase BST and the tungsten bronze phase SBN, are coexistence in BSTNM as they are in BSTN composite ceramics. The Mn ions doped in BSTN substitute for Nb5＋ ions in the tungsten bronze phase, and then, the Nb5＋ ions substitute for Ti4＋ ions in the perovskite phase. With the increasing of Mn dopant, the content of the perovskite phase increases while that of the tungsten bronze phase decreases, and the grain size of the perovskite phase decreases. As well as, the phase transition temperature of tungsten bronze phase increases with value z increasing from 0 to about 0.05.
文摘Composite ceramics of 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 (BSTN) with coexistence of barium strontium titanate, Ba1-xSrxTiO3 (BST), and strontium barium niobate, SrxBa1-xNb2O6 (SBN) phases were successfully prepared in situ by controlling excess components according to a specially designed formula of 0.7BaO·0.3SrO·(1-y)TiO2·yNb2O5 and by using a traditional ceramic process. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersion spectrometer (EDS) were used to characterize the phase composition, morphology and the micro-area chemical composition of the composite ceramics. The results showed that the SBN tungsten bronze phase appeared and coexisted stably with the BST perovskite phase when the excess content of Nb2O5 was >6mol%, whereas the BST perovskite phase formed and coexisted stably with the SBN tungsten bronze phase when the excess content of TiO2 was >5.3mol%. In the case of the two phases being equivalent to each other in BSTN composite ceramics, Nb2O5 was hard to be resolved into the perovskite phase, however, a few of TiO2 was easy to be resolved in the tungsten bronze phase. The microstructure of the composite ceramics were consisted of two kinds of grains. The smaller polygonal grains were belonged to the BST phase, and the larger ones to the SBN phase. The coexistence of the two phases inhibited the growth of the BST crystal. The density of microstructure of the composite ceramic was higher than that of both the pure BST and SBN calcined at the same temperature for the same time.
文摘Strontium barium niobate/barium strontium titanate composite ceramics of xSrO·(1-x)BaO·0.5Nb2O5·0.5TiO2 (BSTN in short) with a range of Sr/Ba ratios were fabricated using a modified sol-gel method with Nb2O5 fine powders suspended in the barium strontium titanate (BST in short) sol solution. Powders obtained from dried gels were calcined at 800 ℃ for 3 h. After preparing bulk ceramics from these powders by sintering at 1200 ℃ for 3 h, the tetragonal tungsten bronze(TTB) phase and perivoskite phase were co-present in compositions between 0.25≤x≤0.75, with the increasing of x value, the peaks of pervoskite phase shift to the high angle position slightly while no changes happened in the peak position of TTB phase. The peak intensity of both two phases were also changed.
