Study on Zn-Nb Series Low Sintering Temperature Microwave Dielectric Material for Applications in Wireless Communication
|Keywords:||Bi1.5Zn0.92Nb1.5O6.92;微波介電性質;低溫燒結;共燒;銀擴散;Zn3Nb2O8;Bi1.5Zn0.92Nb1.5O6.92;silver migration;microwave dielectric property;low sintering temperature;co-fired;Zn3Nb2O8||Issue Date:||2004||Abstract:||
本論文包含三個部分。本論文的第一部分，探討具高品質因子值的Zn3Nb2O8系列陶瓷其物理性質和微波介電性質，相對於純的Zn3Nb2O8要在1150℃下燒結緻密，添加銅鋇助燒結劑（BaCO3-CuO，以下簡稱BC）的3.0wt% BC-added Zn3Nb2O8和銅鉬助燒結劑（MoO3-CuO，以下簡稱MC）的3.0wt% MC-added Zn3Nb2O8，只需在950℃下就可以燒結緻密，且可獲得較佳的微波介電性質。關於銀電極和Zn3Nb2O8系列陶瓷共燒，並未發現新的晶相出現。利用EPMA做線掃瞄分析，Zn3Nb2O8和3.0wt% BC-added Zn3Nb2O8也沒有觀察到銀擴散，但是3.0wt% MC-added Zn3Nb2O8，卻發生輕微銀擴散，其應為MoO3和銀發生反應所造成的。
本論文的第二部分，探討具高介電常數的Bi1.5Zn0.92Nb1.5O6.92（BZN）系列陶瓷其物理性質和微波介電性質，相對於純的Bi1.5Zn0.92Nb1.5O6.92要在1050℃下燒結緻密，添加銅鋇助燒結劑的3.0wt% BC-added BZN只需在950℃下，而添加銅鉬助燒結劑的3.0wt% MC-added BZN在900℃就可以燒結緻密，且可以獲得較佳的微波介電性質。關於銀電極和BZN系列陶瓷共燒，並未發現新的晶相出現，但是利用EPMA做線掃瞄分析，都發現到銀擴散，其應為銀和BZN材料或助燒結劑相互反應所造成的。
最後一部分的研究，利用阻抗儀、網路分析儀和Fourier transform spectrometer研究Bi1.5Zn0.92Nb1.5O6.92的介電行為，Bi1.5Zn0.92Nb1.5O6.92會於低溫時發生介電鬆弛行為，可能是造成其低品質因子值的主要因素。
高介電常數的Bi1.5Zn0.92Nb1.5O6.92可以有效的縮小元件的尺寸，但其助燒結劑會和銀膠發生反應，而導致銀擴散現象，在材料應用前，必須先克服此問題。而3.0wt% BC-added Zn3Nb2O8可以在低溫燒結緻密，擁有高品質因子值特性，且無銀擴散的現象，具有在微波頻段應用的潛力。
Recently, wireless communication systems are growing rapidly to satisfy the personal communication requirements. Compact, small size, low cost, and multi-function are the major developing trends among these modern wireless communication devices. The objective of this thesis is to develop low sintering temperature microwave material which can be cofired with silver electrode.
This thesis consists of three parts. In the first part of the thesis, we investigated systematically the physical properties and microwave dielectric properties in respect to high quality factor value material, Zn3Nb2O8 with sintering aids. For examples of 3.0wt% BaCO3-CuO (BC) mixture added Zn3Nb2O8 and 3.0wt% MoO3-CuO mixture (MC) added Zn3Nb2O8 can be densified at 950℃ with good microwave dielectric properties. The interfacial behavior between Zn3Nb2O8 and silver electrode was investigated. The XRD studies showed no new crystalline phase was found after co-firing pure or doped Zn3Nb2O8 with silver. No migration of silver towards pure Zn3Nb2O8 was observed using electron probe X-Ray microanalyzer (EPMA). However, a slight migration of silver towards MC-added Zn3Nb2O8 was identified. The mechanism of the silver migration was believed to be resulted from the reaction between silver and MoO3.
In the second part of the thesis, we studied systematically the physical properties and microwave dielectric properties of high dielectric constant material, Bi1.5Zn0.92Nb1.5O6.92 (BZN). For example of 3wt% BC-added BZN and 3wt% MC-added BZN at 950℃ can be sintered with higher than 95% densitivity. The optimal amount of dopants is 3wt% of BaCO3-CuO or MoO3-CuO to achieve the best microwave dielectric properties. The dopant concentration was either lower or higher than 3.0wt% would detract the dielectric properties of BZN. The interfacial behavior between BZN series ceramics and silver electrode was investigated. The XRD result showed no new crystalline phase was found after co-firing BZN or doped BZN with silver. The migration of silver towards BZN-based ceramics was observed by EPMA. The mechanism of the silver migration was believed to be resulted from the interaction between silver and sintering aids or BZN material.
In the last part of the thesis, we have studied the dielectric behaviors of Bi1.5Zn0.92Nb1.5O6.92 in detail using impedance analyzer, network analyzer, and Fourier transformed infrared spectrometer. Bi1.5Zn0.92Nb1.5O6.92 exhibited low temperature dielectric relaxation behavior which caused the material to have low quality factor property.
The low sintering temperature 3.0wt% BC-added Zn3Nb2O8 ceramics has a potential for microwave filter applications.
|Appears in Collections:||材料科學與工程學系|
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