稀土氧化物掺杂对BST陶瓷热释电性能的影响

采用轧膜成型工艺制备了掺杂有稀土氧化物的钛酸锶钡(BST)陶瓷,研究了不同稀土(Sc,Y,La,Ce,Pr,Nd和Sm)氧化物掺杂对其微观形貌、介电性能和热释电性能的影响。结果表明,Sc掺杂大幅降低了BST陶瓷的εr,严重劣化了BST陶瓷的热释电性能,并引起了长条状晶粒在BST陶瓷中的出现;Y掺杂则显著提高了BST陶瓷的热释电性能,并最终获得了εr为7111、tanδ为0.65×10–2、热释电系数p为5.5×10–7C·cm–2·℃–1、探测率优值Fd为8.49×10–5Pa–1/2的热释电BST陶瓷材料,有望在红外探测领域得到应用。     

边界扫描测试中几类故障冲突解析

在介绍边界扫描测试应用系统的基础上,结合工程实例研究了边界扫描测试中出现的几类故障冲突,分析了产生的原因,对如何避免、解决此类故障冲突给出了解决方案,对从事该方面的应用测试研究有借鉴作用。     

不同含锰化合物掺杂对BST-MgO陶瓷介电性能的影响

采用普通固相反应法制备了0.45Ba0.55Sr0.45TiO3-0.55MgO-Mn(NO3)2/MnCO3(简称BST-MgO)陶瓷,通过XRD和SEM研究了不同形态含锰化合物(固态MnCO3及液态Mn(NO3)2)掺杂对所制BST-MgO陶瓷致密化及微波介电性能的影响。结果表明,液态Mn(NO3)2掺杂可以增加锰离子进入BST晶格的几率,同时抑制镁离子进入BST晶格,提高BST-MgO陶瓷的致密度,降低介质损耗,获得较高的综合性能:10 kHz下r=116,tan=0.003 8,可调率(Tu)为19.64%,优值K=51.68;3 GHz时Q.f值达788 GHz。     

Microwave Properties of Mn Doped (Ba1 - x,Srx)TiO3Thin Films for Tunable Phase Shifter

Ferroelectric Mn doped Ba_0.5Sr_0.5TiO₃ (Mn-BST) films with/without BaTiO₃ (BT) buffer layer have been grown on (001) MgO substrates by a pulsed laser deposition to investigate electrical tunability at microwave frequencies. Structural properties and surface morphologies of the films were investigated using an X-ray diffractometer and a scanning electron microscope, respectively. Microwave dielectric properties of Mn-BST thin films with BT buffer were studied for reduction of dielectric loss and improvement of electrical tunability. Distributed analog phase shifters have been designed and fabricated on Mn-BST films with/without BT buffer layer to understand microwave dielectric properties. The differential phase shift of the phase shifter fabricated on Mn-BST film was 22° at 10 GHz with 80 V of applied dc bias voltage. In comparison, phase shifter fabricated on Mn-BST/BT multilayers exhibit 41° of differential phase shift at the same condition. This suggests that a BT buffer layer is for microwave tunable device applications. The phase shifter fabricated on Mn-BST/BT multilayers exhibit a low insertion loss (S₂₁) of ?1.1 dB, and a low return loss (S₁₁) of ?14 dB with a bias voltage of 80 V.     

Pyroelectric infrared sensors made of La-modified PbTiO3 thin films and their applications

Abstract

High sensitive pyroelectric infrared (IR) sensors have been fabricated by using c-axis oriented La-modified PbTiO₃ (Pb_1–xLa_xTi_1?x/4O₃, PLT) thin films. The PLT thin films were deposited on (100)-cleaved MgO single crystal substrates by intermittent rf-magnetron sputtering method. The PLT thin films have high figures of merit for IR sensor without a poling treatment. High performance pyroelectric IR sensors (single element type and linear array type) were fabricated by using PLT (x=0·1, γ=5·5x10^?8 C/cm²K, ?_r=200) thin films. The sensors have remarkably high D* of 3–6x10⁸ cmHz^1/2/W and very fast response. A new compact IR sensing system using the linear array sensor (8 elements) has been developed for a new type of room air-conditioner. This system can measure thermal distribution (8x64) by horizontal scanning of the vertical linear array. Image processing with neural network concept makes possible high-accuracy using a few data from the sensor elements. This sensing system provides ‘‘smart airconditioning'’to improve the comfortable control.     

Characterisation and preliminary bioactivity determination of Berberis boliviana Lechler fruit anthocyanins

Berberis boliviana Lechler is a member of the Berberidaceae family that has a small edible red-purple berry. The plant is native to the Peruvian Andes and contains high amounts of anthocyanin pigments. The monomeric anthocyanin content, determined by a pH-differential method, was 7/100 g of seedless berries. Pigments were characterised by HPLC coupled to a photodiode array (PDA) and mass spectrophotometer (MS) detectors. Five aglycones and ten anthocyanins were found and identified as petunidin-3-glucoside (24.4%), delphinidin-3-glucoside (24.1%), malvidin-3-glucoside (22.1%), cyanidin-3-glucoside (10.2%), petunidin-3-rutinoside (7.15%), malvidin-3-rutinoside (4.9%), cyanidin-3-rutinoside (3.8%), delphinidin-3-rutinoside (2.6%), peonidin-3-glucoside (1.1%), and peonidin-3-rutinoside (0.9%).     

快速退火对Pt/BST/Pt电容器结构和性能的影响

采用脉冲激光沉积(PLD)法在Pt/Ti/SiO2/Si(001)基片上制备了Ba0.6Sr0.4TiO3(BST)薄膜,对Pt/BST/Pt电容器在空气中进行400℃快速退火(RTA)处理,研究了快速退火对Pt/BST/Pt电容器的结构和性能的影响。结果表明:快速退火虽然对BST薄膜的结晶质量影响较小,但却极大改善了Pt/BST/Pt电容器的电学性能。当测试频率为100kHz、直流偏压为0V时,介电损耗从快速退火前的0.07减小到0.03,介电常数和调谐率略有增加。快速退火后负向漏电流过大现象得到了明显抑制,正负向漏电流趋于对称,在300×103V/cm电场强度下,漏电流密度为4.83×10–5A/cm2。     

The properties of Ba0.5Sr0.5TiO3 thin film prepared by RF magnetron sputtering from powder target

The Ba_0.5Sr_0.5TiO₃ (BST) thin film with the thickness of 400 nm deposited from powder target is prepared by the radio-frequency magnetron sputtering technique. The deposition rate of BST film is estimated to be 45 nm/min, which is very fast for ferroelectric materials. The dielectric properties of the as-prepared BST thin film are demonstrated. High dielectric tunability up to 42.7% and low dielectric loss small to 0.01 are achieved at a low applied voltage of 5 V. The results demonstrate that the RF magnetron sputtering from powder target is a versatile, novel technique for the deposition of high-quality ferroelectric thin films.     

Structure and electrical properties of Ba0.67 Sr0.33TiO3 thin film fabricated by sol-gel based composite technique

A sol-gel based novel technique is used to fabricate Ba_0.67Sr_0.33TiO₃ (BST) thin films with thickness up to several microns. In this technique, surface-modified fine BST particles are dispersed in a sol-gel precursor solution. The pH value of the precursor solution is modified to achieve high zeta potential for the dispersed powder, hence a very stable and uniform slurry can be produced. The slurry is then spin-coated onto Pt/Ti/SiO₂/Si substrate, pre-heated and annealed as in conventional sol-gel process. The resulting films show well-developed dense polycrystalline structure with uniform grain distribution. The metal-BST-metal structure of the films displays good dielectric properties.     

Pyroelectric and dielectric properties of sol–gel derived barium–strontium–titanate (Ba0.64Sr0.36TiO3) thin films

The barium–strontium–titanate (BST, Ba_0.64Sr_0.36TiO₃) thin films have been prepared by the sol–gel method on a platinum-coated silicon substrate. The resulting thin films show very good dielectric and pyroelectric properties. The dielectric constant and dissipation factor for Ba_0.64Sr_0.36TiO₃ thin film at a frequency of 200 Hz were 592 and 0.028, respectively. The dependence of the capacitance as a function of the voltage shows a strongly non-linear character, and two peaks characterizing spontaneous polarization switching can be clearly seen in this curve, indicating that the films have a ferroelectric nature. The capacitance changed from 495 to 1108 pF with the applied voltage in the −5 to +5 V range at a frequency of 100 kHz. The peak pyroelectric coefficient at 30 °C is 1080 μC/m² K. The pyroelectric coefficient at room temperature (25 °C) is 1860 μC/m² K, and the figure-of-merit of this film is 37.4 μC/m³ K. The high pyroelectric coefficients and the greater figures-of-merit of Ba_0.64Sr_0.36TiO₃ thin films make it possible to be used for thermal infrared detection and imaging.