• Korean Journal of Materials Research
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• v.13 no.9
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.17-22
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• 2004

The microwave dielectric properties of $CaZrO_3$ ceramics with addition of $CaTiO_3$ were studied. The effect of glass addition on the low-temperature sintering and microwave dielectric properties of $CaZrO_3-CaTiO_3$ ceramics were also evaluated to develop the materials for functional substrates of low-temperature co-fired ceramics. When $10-20 wt\%$ of lithium borosilicate glass was added, the sintering temperature of the $CaZrO_3-CaTiO_3$ ceramics decreased from $1450^{\circ}C$ to below $900^{\circ}C$. As the $T_f$ of glass frits and $CaZrO_3$ are slightly negative and that of $CaTiO_3$ is significantly positive, zero $T_f$ could be realized by mixing an appropriate amount of $CaTiO_3$ with $CaZrO_3$. The $CaZrO_3-CaTiO_3$ ceramics sintered at $875^{\circ}C$ with $15wt\%$ glass frits showed the relative density of $98\%$, permittivity of 23, quality factor of 2500 GHz, and temperature coefficient of resonant frequency of $ -3 ppm/^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.30 no.8
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• pp.635-642
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• 1993

To obtain a higher dielectric constant material, we investigated Ca substitution for Pb in PbZrO3. In this study, the four mixtures of (Pb0.68Ca0.32)ZrO3, (Pb0.65Ca0.37)ZrO3, (Pb0.63Ca0.37)ZrO3, and (Pb0.60Ca0.40)ZrO3 were prepared by coprecipitation reaction of Pb(NO3)2, ZrOCl2, and CaCl2 with (NH4)2CO3 and NH4OH in aqueous solution. The (Pb1-xCax)ZrO3 with different x mole fractions (x=0.35, 0.37) showed not only high dielectric constant, but also high Q values and low temperature coefficient of the capacitance.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.104-114
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• 1994

ZrO2 fibers were fabricated by means of the Sol-Gel process using Zr(O-nC3H7)4-H2O-C2H5OH-HNO3 solution as a starting material. The optimum experimental parameters such as molar ratio of starting materials, concentration, temperature, viscosity, the amounts of stabilizer and the pH of solution were determined. The experimentally determined optimum variables which produce good ZrO2 fibers were used to manufacture the Y2O3-and CaO-ZrO2 fibers. The amounts of Y2O3 and CaO were varied within the range from 1.5~5 mol% and 3~15 mol% respectively. The phase transformation and microstructural evolution of the fabricated ZrO2 gel fibers were investigated after heat treatments up to 120$0^{\circ}C$ by X-ray diffraction, Raman microprobe spectroscopy, SEM, and specific surface area and pore volume measurements. From the analysis of X-ray diffraction and Raman spectra, the phase of heat treated Y2O3-and CaO partially stabilized ZrO2 gel fibers(Y2O3:2.5~3 mol%, CaO:6~9 mol%) were identified as a tetragonal phase up to 100$0^{\circ}C$. The maximum tensile strength of 2.5Y2O3-97.5ZrO2 and 6CaO-94ZrO2 (in mol%) fibers heat treated at 100$0^{\circ}C$ for 1 hr was found be 1.3~2 GPa with diameters of 10~20 ${\mu}{\textrm}{m}$.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.145-156
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• 1997

ZrO2 phase transformations depending on the type and amount of dopants and the sintering temperatures were studied for the 2 components (CaO-, Y2O3-, MgO-ZrO2) and the 3 components(MgO-ZrO2-Al2O3)ZrO2 powder by X-ray diffraction and Raman spectroscopy. In the CaO- and Y2O3-ZrO2 systems, as the CaO and Y2O3 contents increased to 6~15mol% and 3~15mol% respectively, we were not able to identify between tetragonal and cubic in the X-ray diffraction patterns. On the other hand, all Raman modes shifted to lower wavenumbers, decreasing in intensity and the number of bands, markedly. These phenomena were caused by tetragonallongrightarrowcubic phase transformation and interpreted by the breakdown of the wave vector selection rule(k=0) and the structural disorder associated with the formation of oxygen sublattice which was caused by the substitution between Zr4+ ion and Ca2+ or Y3+ ion in ZrO2 matrix. The monoclinic to cubic phase transformation occurred in 10mol% MgO-ZrO2 system. As the Al2O3 content increased from 0 to 20mol% in the MgO-ZrO2-Al2O3 systems, cubic phase transformed to monoclinic phase, this is because the MgO didn't play a role in a stabilizer because of the formation of the spinel(MgAl2O4) by the reaction between MgO and Al2O3, Also, the ZrO2 phase transformation was explained by the change of it's lattice parameters depending on the type and amount of dopants. Namely, as the amount of dopant increased to 10~13mol%, the axial ra-tio c/a came close to unity with increasing the lattice parameter a and decreasing the lattice parameter c. At that time, the tetragonallongrightarrowcubic phase transformation occurred.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.228-232
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• 2021

Ca_1-xZrO₃:xPr phosphor with perovskite structure was successfully synthesized by using skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet fluorescence reaction and photoluminescence. The XRD results indicated that single crystals of CaZrO₃:Pr³⁺ belongs to orthorhombic perovskite system. The synthesized phosphor could be excited by UV light (254 nm) and the emission spectra results indicated that green luminescence of CaZrO₃:Pr³⁺ due to charge transfer transition ³P₀ → ³H₄, ³P₁ → ³H₅ and ³P₀ → ³H₅ at 506, 536 and 548 nm was dominant.

• Electrical & Electronic Materials
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• v.10 no.6
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• pp.533-540
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• 1997

The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.27-32
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• 2008

Novel long persistent phosphors of $CaZrO_3:Er^{3+}$ have been synthesized by traditional solid state reaction method. The long persistent phosphor crystalline particles were characterized by the X-ray diffraction (XRD), photoluminescence spectrophotometer, thermoluminescence (TL) and luminance meter. The results reveal that the samples are composed of single $CaZrO_3$ phase. The broadband emission spectra of 446 nm peak and 550 nm peak was revealed by synthesized at high temperature in $N_2$ gas. Green long persistent phosphors have been observed in the sys_em for over 6 h after UV irradiation (254 nm). The main emission peak was ascribed to $Er^{3+}$ ions transition from $^5D_{5/2}{\rightarrow}^4F_{9/2},\;^2H_{12/2},\;^4S_{3/2}{\rightarrow}^4I_{13/2}\;and\;^2G_{9/2}{\rightarrow}^4I_{13/2}$, and the afterglow may be ascribed to the suitable trap centers in the $CaZrO_3$ host lattice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.635-638
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• 2004

페로브스카이트 구조를 가지는 $CaZrO_3$ 유전체 세라믹스에 $CaTiO_3$를 부피 비율로 첨가하여 첨가량 변동에 따른 마이크로파 유전 특성을 조사하였다. 또한 저온 동시소성 기능성 LTCC 기판용 유전체 소재로서 활용하기 위하여 저융점의 borosilicate계 유리 프리트를 첨가하여 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스의 저온 소결 거동과 마이크로파 유전 특성을 평가하였다. 알칼리가 첨가된 저융점의 borosilicate계 유리 프리트를 $10\sim30$ wt% 범위로 첨가함으로서 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스의 소결온도를 $1450^{\circ}C$에서 $900^{\circ}C$이하로 낮출 수 있었으며, 유리 프리트의 첨가량으로 공진 주파수 온도계수 특성을 조절할 수 있었다. 유리 프리트의 첨가량이 15 wt% 첨가시 $875^{\circ}C$에서 충분한 소결이 이루어졌으며, 이 경우 $CaZrO_3-CaTiO_3$ 복합 유전체 세라믹스는 유전율(k) 23, 품질계수(Qxf) 2500, 공진 주파수 온도계수 ($\tau_{cf}$) -3 ppm/$^{\circ}C$의 매우 양호한 마이크로파 유전 특성을 나타내었다. 유리 프리트의 첨가에 의하여 소결 과정에서 주상인 $CaZrO_3$가 $CaZr_4O_9$ 상으로의 변화가 뚜렷이 나타났는데, 이러한 상전이 현상과 함께 미세구조의 변화에 대해서도 고찰하였다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.5
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• pp.30-35
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• 1993

We have investigated microwave dielectric properties of TiO$_{2}$ added (Pb$_{1-x}$Ca$_{x}$)ZrO$_{3}$ Ceramics with x=0.33, 0.35, and 0.37 sintered at 1400$^{\circ}C$ for 2 h. For additions of up to 3wt% of TiO$_{2}$ in (Pb$_{0.63}$ Ca$_{0.37}$)ZrO$_{3}$ (x=0.37), TiO$_{2}$ was completely soluble in (Pb, Ca)ZrO3 phase and did not affect the grain size of ceramics. Dielectric constant and temperature coefficient of resonant frequency increased due to the formation of solid solution, whereas Q value decreased linearly as TiO$_{2}$ increased up to 1 wt%. However, the dielectric loss was very high as TiO$_{2}$ exceeded 2 wt%. It was also shown that as Ca ion content in 0.5 wt% TiO$_{2}$ added (Pb$_{1-x}$,Ca$_{x}$)ZrO$_{3}$ decreased from x=0.37 to x=0.33, dielectric constant increased and Q value decreased.