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  • 學位論文

參雜氧化鈮之鋯鈦酸鉛靶材及其薄膜之製程與性質分析

Investigation on Processing and Properties for Nb2O5 doped PZT Targets and Thin Films

指導教授 : 韋文誠

摘要


本研究主要探討鋯鈦酸鉛添加氧化鈮之靶材以及其薄膜之製程,燒結性質與電性。在塊材製程方面,其程序為將陶瓷粉體分散於特定溶液後高壓注漿成形,由於鋯鈦酸鉛分散於水溶液時,粉體表面之鉛成分極易溶出形成鉛離子,進而影響鋯鈦與鉛原有氧化物之劑量比,所以本研究選用,甲苯,二丁酮,以及正庚烷,並添加數種分散劑,作為鋯鈦酸鉛以及氧化鈮粉體之分散劑。由沉降實驗,生胚密度,ζ-電位儀以及原子吸收光譜儀之結果,選出添加0.6 wt%之分散劑KD4結合甲苯作為分散鋯鈦酸鉛為最佳系統。接著利用高壓注漿成形得到生胚後,於1200 oC燒結得到高緻密度高純度之PZT以及PNZT塊材。由XRD,及SEM觀察其顯微結構及結晶相,添加氧化鈮後,當鈮添加量小於4.7 mol%,PNZT晶粒較小且孔隙率較大,密度下降。當添加量大於4.7 mol%後,則呈相反趨勢。塊材鐵電性則利用鐵電分析儀 (TF analyzer 2000)測得遲滯曲線,以及交流阻抗分析儀之結果,計算得各壓電係數及機電耦合常數,結果顯示微結構中鉛空缺數量之提升效應(添加鈮量)主要為降低矯頑電場(Ec),而屬於立方晶相之pyrochlore之存在以及添加鈮後縮小之粒徑將使得d33,d31,Kp以及殘餘極化量下降。 在薄膜製程方面,將前階段製備出之塊材作為PZT以及PNZT鈀材,利用離子束濺鍍法將PZT以及PNZT薄膜沉積於未加熱之白金/鈦/矽晶圓(Pt/Ti/Si),後續熱處理溫度選擇600以及700 oC。製備後薄膜利用XRD,SEM,TEM以及AFM,進行膜厚量測,膜成分,微結構以及結晶相分析。結果顯示熱處理溫度700 oC,PZT及PNZT薄膜方可轉換為pervoskite結晶相,而由於PNZT膜中之鈮含量為8.63 mol%,超過鈮於PZT之溶解度,產生第二相(pyrochlore結晶相)。PZT以及PNZT薄膜微結構由TEM以及SEM觀察,熱處理後,濺鍍八小時得到膜厚皆約為2.2 μm,而PZT薄膜後之晶粒成長呈現110優選方位(preferred orientation),晶粒大小約為2μm,但PNZT薄膜晶粒尚有第二物殘留,且晶粒較小,此外,薄膜內部皆有分布均勻之孔洞形成,底部白金電極因表面張力效應(或稱Rayleigh effect)之擴散作用,無法形成連續膜。遲滯曲線結果顯示,相較於過去文獻,雖本製程可得到大晶粒之PZT以及PNZT薄膜,但殘餘極化值卻較低,且矯頑電場又較高,比較由塊材所得之微結構與電性之關係,推測殘餘極化值之衰減及矯頑電場之提升,主要應由薄膜中之孔洞及其他為結構因素所造成。

並列摘要


Processing and properties for the preparation of Nb doped PZT targets and thin films were investigated. The microstructural related electrical properties were determined in this research. The PZT or PNZT bulk materials were fabricated by colloid processes in which the ceramic powders had to be dispersed into particular solvents. In order to prevent the dissolution of Pb species dissolving from PZT powder in aqueous dispersion systems, several organic dispersion systems were used. From the analysis of atomic absorbance spectroscopy, centrifugal sedimentation and ζ-potential, 0.6 wt% KD4 added toluene was an optimum dispersion system for PZT and Nb2O5 powders. SEM and XRD were used to analyze the microstructure and crystalline phase of PZT and PNZT bulk materials. The solubility limit of Nb in PZT were found to be 5 mol% in this research. The grain sizes of PNZT decreased as the Nb concentration below 4.7 mol%, while contrary trend could be noted at the doping concentrations higher than this value. It was found that the amount of Nb doping, could reduce the value of coercive field. Otherwise, the existence of pyrochlore phase and inhibited grain sizes would cause the value of d33,d31,Kp and Pr decreasing. The PZT and PNZT thin film materials were deposited on Pt/Ti/Si at ambient temperature by ion beam sputtering deposition (IBSD) and the annealing temperatures, 600 and 700 oC were chosen. XRD, AFM, SEM, and TEM were used to analyzed film thickness, crystal phase, Nb content and microstructure. The results shown that the annealing temperature should be 700 oC was good for PZT thin film to crystallize into pervoskite phase, while for PNZT thin film, second phases (pyrochlore) were existed. After full quantification of PNZT film by EDS, the Nb content was about 8.63 mol% which was higher than the solubility limit of Nb in PZT material. From TEM results, the grain sizes of PZT thin film were about 2 μm with an (110) preferred orientation. As for PNZT thin film, grain sizes in equiaxial were about 1 μm with randomly orientation. Porosity was noted inside these films and the discontinuities of Pt electrode were occasionally seen in PZT and PNZT thin films. The results of D-E loops for both PZT and PNZT thin film revealed lower Pr and higher Ec by comparing with the commonly observed value, 30-70 C/m2, though the grain sizes were larger and the crystal phases were pervoskite phase. This degraded polarization behavior of PZT and PNZT thin films, the same as that observed in PZT and PNZT bulk materials, should be caused by the existence of pores and the other structural features in both films.

並列關鍵字

Niobium PZT Zeta potential Pb dissolution target thin film IBSD

參考文獻


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