材料物理性能習(xí)題缺熱電學(xué)英文

1、材料物理性能習(xí)題目錄材料物理性能習(xí)題1電介質(zhì)1光學(xué)2磁學(xué)3電介質(zhì)1 Briefly explain how the charge storing capacity of a capacitor may be increased by the insertion and polarization of a dielectric material between its plates.2 非晶態(tài)硒是一種高電阻率的半導(dǎo)體，其密度約為4.3g/cm-3，原子序數(shù)為34，相對原子量為78.96，其在1kHz下的相對介電常數(shù)為6.7。計算施加在每個原子上的局部電場Eloc相對宏觀電場E的大小。局部場大還是

2、外加電場大?如果設(shè)局部電場等于外加電場,請給出克勞修斯-莫索蒂方程的表達(dá)式.3Ionic and electronic polarization Consider a CsBr crystal that has the CsCl unit cell crystal structure (one Cs+-Br- pair per unit cell) with a lattice parameter (a) of 0.430 nm. The electronic polarizability of Cs+ and Br- ions are 3.35 ´ 10-40 F m2 and 4

3、.5 ´ 10-40 F m2, respectively, and the mean ionic polarizability per ion pair is 5.8 ´ 10-40 F m2. What is the low frequency dielectric constant and that at optical frequencies? Is the dielectric constant in low frequency and optical frequency the same? Why？4. (a) For each of the three typ

4、es of polarization, briefly describe the mechanism by which dipoles are induced and/or oriented by the action of an applied electric field.(b) For solid lead titanate (PbTiO3), gaseous neon, diamond, solid KCl, and liquid NH3, what kind(s) of polarization is (are) possible? Why? 提示:查材料的介電性能的參考書,并且在作

5、業(yè)中寫出所查參考書名字,頁數(shù). 5.查文獻(xiàn),描述偶極子轉(zhuǎn)向極化的過程(參照課堂上給出的熱離子松弛極化描述過程：沒有加電場的狀態(tài)，加電場后的運動過程，最后的狀態(tài))orientation polarization, is found only in substances that possess permanent dipole moments. Polarization results from a rotation of the permanent moments into the direction of the applied field, as represented in Figure

6、 18.32c. This alignment tendency is counteracted by the thermal vibrations of the atoms, such that polarization decreases with increasing temperature.Response of permanent electric dipoles (arrows) to an applied electric field, producing orientation polarization.6根據(jù)德拜方程，查閱資料，說明頻率、溫度對介電常數(shù)的實部、虛部和損耗角正切

7、的影響。7.限本章教學(xué)內(nèi)容范圍,提出一個自己不懂的問題8.思考題(選作)結(jié)合材科基課程中玻璃的結(jié)構(gòu)知識,查文獻(xiàn),舉例說明引起結(jié)構(gòu)損耗以及中和效應(yīng)的原因的具體來源 某介質(zhì)的es=10, e=2, t=10-10s，請分別畫出e、e以及tan隨lg變化曲線，在曲線上標(biāo)出tan和e峰值的位置， e max等于多少？光學(xué)1 太陽能電池中的增透膜： 當(dāng)光照射到半導(dǎo)體表面時，光被部分反射。在太陽能電池中，進(jìn)入半導(dǎo)體器件中的透射光能量被轉(zhuǎn)換為電能。所以被部分反射的光是需要重點考慮的因素。波長700-800nm附近的硅的折射率約為3.5，（a）求對于n1(空氣）=1和n2(Si)=3.5的反射系數(shù)。（b） 查

8、資料尋找用于降低在硅和空氣之間的反射率的增透膜材料和使用了增透膜之后的反射率.2.已知折射率 ,折射率隨介電常數(shù)增大而增大,根據(jù)已經(jīng)學(xué)習(xí)的電介質(zhì)材料性能,從介電常數(shù)和材料結(jié)構(gòu)的關(guān)系角度,簡單說明折射率和材料結(jié)構(gòu)的關(guān)系3. Cauchy dispersion relation for zinc selenide ZnSe is a II-VI semiconductor and a very useful optical material used in various applications such as optical windows (especially high power las

9、er windows), lenses, prisms etc. It transmits over 0.50 to 19 µm. n in the 1 11 µm range described by a Cauchy expression of the formin which is in µm. What is ZnSe's refractive index n at 5 µm and 8µm?4.有一光釬的釬芯和包層的折射率分別為n1和n2，n1和n2分別是1.455和1.440，求能夠在光釬中傳播的入射光與釬軸向的夾角最大是多

10、少？ 查出一種已經(jīng)商用化的通訊用光纖的以下資料: 名稱，型號，釬芯和包層的折射率;目前傳導(dǎo)的光的波長是多少? 制備光纖的材料,衰減特性，造成光纖傳導(dǎo)衰減的原因.5.Gallium arsenide (GaAs) and gallium phosphide (GaP) are compound semiconductors that have room-temperature band gap energies of 1.42 and 2.25 eV, respectively, and form solid solutions in all proportions. Furthermore,

11、the band gap of the alloy increases approximately linearly with GaP additions (in mol%). Alloys of these two materials are used for light-emitting diodes wherein light is generated by conduction-band-to-valence-band electron transitions. Determine the composition of a GaAsGaP alloy that will emit or

12、ange light having a wavelength of 0.60m. 6.查資料,以一個具體材料為例,簡單說明利用拉曼散射鑒別材料微結(jié)構(gòu)的原理7.查資料說明用異質(zhì)結(jié)來增加LED器件輸出光強(qiáng)度的原理.8. 就本章教學(xué)內(nèi)容,提出一個自己不懂的問題9.解答電介質(zhì)一章同學(xué)提出的問題磁學(xué)1.Briefly explain the nature and source of (a) diamagnetism, (b) paramagnetism, and (c) ferromagnetism. 2. Compute the atomic magnetic moments of the rare

13、earth Nd metal and metal Co。3. Compute the molecular magnetic moment of CoFe2O4 ferrite，Its magnetic structure is: (Fe3+)Co2+Fe3+O44. Compute Bohr magnetons associated with each iron atom, given that the saturation magnetic polarization is 2.2T(J=m0M). The density of iron is 7.87g/cm3.5. Briefly exp

14、lain why the magnitude of the saturation magnetization decreases with increasing temperature for ferromagnetic materials, and why ferromagnetic behavior ceases above the Curie temperature.6. Explain a difference of the magnetization curves of the polycrystalline magnetic bar in figure 2.1 when the m

15、agnetic field was applied at different direction。7.查資料，簡述一種利用控制成分或者結(jié)構(gòu)降低磁性材料磁晶各向異性的方法。8已知單位體積鐵磁性材料的退磁能可以寫成：求有如下體積的單晶鐵的退磁能：(a)具有單疇的1*1*1cm3塊體以及直徑為1*10-9m的小球9。利用表3-6，計算直徑為1*10-9m的小球中存在圖3-32(a)的磁疇時的疇壁能大小。比較第8題和第9題結(jié)果，你認(rèn)為直徑為1*10-9m的小球?qū)嶋H存在的磁疇結(jié)構(gòu)是單疇還是如圖3-32(a) 那樣的疇？10. What kind of the magnetic domain config

16、uration may forms for iron and cobalt metal balls in figure 8 if only the magnetocrystalline anisotropy is considered? Fig.811。The following data are for a transformer steel:(a) Construct a graph of B versus H.(b) What is the value of the maximum permeability?(c) At about what H field does this maxi

17、mum permeability occur?(d) To what magnetic susceptibility does this maximum permeability correspond?12. 根據(jù)給定的H-Bdata中的數(shù)據(jù)，把H的單位換成Oe,計算: （1）做H-B圖； （2）求出Br,Hc,Bs值，并且標(biāo)在圖上； （3）求H-B曲線第二象限的BH值，并做H-BH圖，求出(BH)max,在圖上標(biāo)出該點。 （4）結(jié)合教科書和查資料,敘述如何提高Br,Hc?13. (a) Describe magnetic hysteresis; (b) explain why ferromagnetic and ferrimagnetic mater