• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.101-103
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• 2003

The $ZnNb_2O_6$ ceramics with 5wt% CuO and $B_2O_3$(1,3,5wt%) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $950^{\circ}C{\sim}1025^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature and $B_2O_3$ addition by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature and $B_2O_3$ addition. Increasing the sintering temperature, the peak of second phase ($Cu_3Nb_2O_6$) was increased. But no significant difference was observed as the $B_2O_3$ addition, In the $ZnNb_2O_6$ ceramics with 5wt% CuO and 5wt% $B_2O_3$ sintered at $975^{\circ}C$ for 3hr, the dielectric constant, quality factor, temperature coefficient of the resonant frequency were 19.30, 14,662GHz, $+4.18ppm/^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1335-1341
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• 1999

The electrical conductivity ($\sigma$) of TiO2 doped with 0.05-4.0mol% Nb2O5 was measured in the oxygen partial pressure range of 10-17 to 100 atm and temperature range of 1100 to 130$0^{\circ}C$ to investigate the electrical properties and defect types. The oxygen partial pressure dependence of the electrical conductivity (log$\sigma$/logPo2) above 110$0^{\circ}C$ was divided into the four regions. From these experimental results the following defect regions were proposed ; 1) Magneli phase(extended defect) 2) reduced rutile region where intrinsic defect predominates 3) nearly stoichiometric region which is independent on the oxygen partical pressure and 4) overstoichiometric region which is not observed in pure TiO2 The electrical conductivity of Nb-doped TiO2 depended on the doping content the oxygen partial pressure and the measuring tem-perature.

• Journal of the Korean institute of surface engineering
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• v.33 no.4
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• pp.251-260
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• 2000

Ta and Hf added Ti-l5Sn-4Nb alloys without V and Al elements for biomaterial were melted by arc furnace in response to recent concerns about the long term safety of Ti-6Al-4V alloy. All specimens were homogenized at $1000^{\circ}C$ and solution treatment was performed at $812^{\circ}C$ and aging treatment at $500^{\circ}C$. The microstructure and mechanical properties were analysed by optical micrograph, hardness tester and instron. Ti-l5Sn-4Nb system alloys showed widmanstatten microstructure which is typical microstructure in $\alpha$＋$\beta$ type Ti alloys. The Ti-l5Sn-4Nb-2Hf and Ti-l5Sn-4Nb-2Ta alloys showed better hardness and tensile strength compared with Ti-6Al-4V. The result of XPS analysis, Ti-l5Sn-4Nb alloy in air atmosphere consisted of $TiO_2$, SnO and NbO.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.346-349
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• 2003

Microwave dielectric characteristics and physical properties of the new Zr$_{1-x}$ (Bn$_{1}$3/Nb$_{2/3}$)xTi $O_4$ (0.2$\leq$x$\geq$ 1.0) system have been investigated as a function of the amount of Bn$_{1}$3/Nb$_{2/3}$ $O_2$substitution. With increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ content (x), two phase regions were observed: $\alpha$-Pb $O_2$ solid solution (x<0.4), mixture of the rutile type Zn$_{1}$3/Nb$_{2/3}$Ti $O_4$ and the $\alpha$-Pb $O_2$ solid solution (x$\geq$0.4). In the$\alpha$-Pb $O_2$solid solution region below x<0.4, the Q.f$_{0}$ value sharply increased and the Temperature Coefficient of the Resonant Frequency(TCF) decreased with increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ contents while dielectric constant (K) showed nearly same value. In the mixture region above x$\geq$4, the dielectric constant and TCF increased with increasing Bn$_{1}$3/Nb$_{2/3}$ $O_2$ content. Zr$_{1-x}$ (Zn$_{1}$3/Nb$_{2/3}$)xTi $O_4$ materials have excellent microwave dielectric properties with K=44.0, Q.f$_{0}$ : 41000 GHz and TCF =-3.0 ppm/$^{\circ}C$ at x=0.35.=0.35. x=0.35.=0.35.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.915-920
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• 1997

Tetragonal ZrO2 polycrystal (TZP), consisted of 90.24 mol% ZrO2-5.31 mol% Y2O3-4.45 mol% Nb2O5, were prepared using hot-press and mechanical properties and high-temperature degradation were investigated. The specimen, hot-pressed for 1 h at 140$0^{\circ}C$ in Ar atmosphere, exhibited flexural strength of 1010 MPa and fracture toughness of 7.5 MPam1/2 and experienced no low-temperature degradation below 40$0^{\circ}C$. However, as aged for 100h at temperatures higher than 40$0^{\circ}C$, TZP was suffered by high-temperature degradation due to an extensive cavitation caused by the oxidation of carbon. XPS observation revealed that the carbon incorporated in TZPs during hot-pressing exists as either an ether-type CO or a carbonyl-type C=O. Despite of the high-temperature degradation of t-ZrO2 co-doped with Y2O3 and Nb2O5, its flexural strength and fracture toughness were superior to those of the commercial 3 mol% Y2O3-TZP hot-pressed under the identical condition as determined before and after the aging treatments.

• Journal of the Korean Ceramic Society
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• v.25 no.4
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• pp.335-340
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• 1988

The change in microstructure and the electrical properties of Pb(In1/2Nb1/2)O3-PbTiO3 Ceramics caused by V2O5 addition were studied. The results are ; 1. interability was increased because the mass transport through the second phase formed by V2O5 addition increased. 2. ith addition of V2O5, tetragonality and Curie temperature increased. The maximum value of kp was observed when 0.5wt% of V2O5 was added. 3. he second phase formed by V2O5 accelerated the grain growth, and existed in grain boundary. Electrical properties were changed by corelations between tetragonality and the amount of second phase.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.116-121
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• 1999

0.5 wt%Nb-doped SrTiO3(Nb: STO) thin film was prepared on MgO(100) single crystal substrates by Pulsed Laser Deposition (PLD). The Crystallinity and the orientation of Nb:STO thin films were characterized by XRD with changing the thin film processing condition-oxygen partial pressure, substrate temperature, deposition time and the distance between target and substrate. The orientation of Nb:STO thin film showed (100), (110) and (111) orientations at the substrate temperature of $700^{\circ}C$. The lattice parameter of Nb:STO decreased with increasing Po2 and showed 0.3905 nm at Po2=100 Pa, which was similar to that of the bulk. The thickness of Nb:STO thin film increased with increasing the deposition time and with decreasing the distance between target and substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.661-664
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• 1999

The piezoelectric properties and the doping effect of Nb$_2$O$_{5}$ for 0.95 PbZr$_{x}$ Ti$_{1-x}$ -O$_3$+0.05 Pb(Mnsub 1/3/Nb$_{2}$3/)O$_3$ compositions have been investigated. In the composition of 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$ the values of k$_{p}$ and $\varepsilon$$_{33}$ $^{T}$ are maximized, but Q$_{m}$ was minimized (k$_{p}$ =0.57, Q$_{m}$ =1550). The grain size was suppressed and the uniformity of grain was improves with doping concentration of Nb$_2$O$_{5}$ far 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$. sample. The values of k$_{p}$ first decreased slightly when a small amount of Nb$^{5+}$ is doped and then decreased when the Nb$^{5+}$ concentration is further increased. The Q$_{m}$ . OR the Other hand. increased monotonously with doping concentration of Nb$_2$O$_{5}$ .{5}$ . .

• Bulletin of the Korean Chemical Society
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• v.23 no.10
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• pp.1463-1482
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• 2002

Partially doped Aurivillius phases SrBi2N$b_{2-x}M_xO_9$ (M=Cr and Mo) were successfully synthesized and characterized. The extent of the substitution was limited at ~20 mole % because of the size differences between $Nb^{5+}$ and $Cr^{6+}$, and between $Nb^{5+}$ and $Mo^{6+}$. When the amount of substitution exceeded ~20 mole%, the phases began to collapse and the second phases were made. The dielectric constants of substituted compounds were enlarged nevertheless Cr or Mo is substituted. The increment is bigger in the Mo substituted compound than in the Cr doped one although the Nb(Cr)$O_6$ octahedra could be more strongly distorted than the Nb(Mo)$O_6$ octahedra since the ionic size difference between $Nb^{5+}$ and of $Cr^{6+}$ is much bigger than that between $Nb^{5+}$ and $Mo^{6+}$. Consequently, the dielectric constant of the substituted Aurivillius phase $Bi_2$A_{n-1}B_{n-x}M_xO_{3n+1}$$ depends on the extent of distortion of the B$O_6$ octahedra and more strongly on the polarizability of the metal.

• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.100-105
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• 1998

This paper describes the preparation of Pt-and $TiO_2$-doped $Nb_2O_5$ thin film by Ion-Beam-Enhanced Deposition. Platinum and titanium doping, and Nb2O5 deposition were carried out in situ. The dependence of oxygen sensing properties on the amounts of Pt and Ti dopant in the $Nb_2O_5$ film was investigated. There were the highist sensitivity, the lowest temperature coefficient and the shortest responce time at doping of 5 mol% $TiO_2$ and 0.3 mol%Pt