The electrical properties of a laminated SMD type PTC thermistor for microcircuit protection were investigated as a function of polymer blowing agent addition. Green ceramics for multilayered BaTiO3-based PTCRs were formed by doctor blade method of barium titanate powders; we successfully laminated the sintered ceramic chips to obtain 10 layer chip PTCRs with PTC effect. The sintered density increases with increasing sintering temperature. The electrical properties of the sintered samples were strongly dependent on the calcination and addition of a polymer blowing agent. When BaTiO3 powders containing 0.2 mol% of Y2O3 were calcined at 1000˚C for 2 hrs, the resistivity jump was of 1-2 orders of magnitude. The resistivity at room temperature increases according to the polymer blowing agent addition. Also, the sample using the calcined powder showed a lower resistivity than that of the sample prepared using powders without calcinations. With an increase in the OBSH, the magnitude of the resistivity jumped as a function of the temperature increase. The resistivity of the sintered bodies after the addition of 0.5 wt% polymer blowing agent at 1290˚C for 2 h was shown to be about 8.5Ω·cm; the jump order of the sintered bodies was shown to be on the order of 102.

The influences of Na and K content on the crystal phase, the microstructure and the electrical property of BaTiO3-based thermistors was found to show typical PTC effects. The crystal phase of powder calcined at 1000˚C for 4hrs showed a single phase with BaTiO3, and the crystal structure was transformed from tetragonal to cubic phase according to added amounts of Na and K. In XRD results at 43˚~47˚, the (Ba0.858Na0.071K0.071)(Ti0.9985Nb0.0015)O3-δ showed (002) and (200) peaks but the (Ba0.762Na0.119K0.119)(Ti0.9975Nb0.0025)O3-δ showed (002), (020) and (200) peaks. In sintered bodies, those calcined at 600˚C rather than at 1000˚C were dense, and for certain amounts of Na and K showed rapid decreases in grain size. In relative permittivity, the curie temperature due to the transformation of ferroelectric phase rose with added Na and K but decreased in terms of relative permittivity. In the result of the R-T curve, the sintered bodies have curie temperatures of about 140˚C and the resistivity of sintered bodies have scores of Ω·cm; the jump order of sintered bodies was shown to be more than 104 in powder calcined at 1000˚C.

In this study, the effects of carbon black (CB) content and anodic oxidation treatment with AgNO3 on positive temperature coefficient (PTC) behavior of CB/HDPE nanocomposites were investigated. Also, the addition of elastomer as a toughing agent was studied. The 20~50 wt% of CB, 0~5 wtt% of elastomer, and 1 wt% of AgNO3-filled HDPE nanocomposites were prepared using the internal mixer in 60 rpm at 160˚C and the compression-molded at 180˚C for 10 min. As a result, the room temperature resistivity and PTC intensity of the composites were dependent, to a large extent, on the content of CB, addition of elastomer, and surface chemical properties that were controlled in the relative arrangements of the carbon black aggregates in a polymeric matrix. Moreover, the composites with relatively low room temperature resistivity and suitable PTC intensity could be achieved by treatment of AgNO3. Consequently, it was noted that PTC effect was due to the deagglomeration or the breakage of the conductive networks caused by thermal expansion or crystalline melting of the polymeric matrix.

Circuitry to be connected to a Telecommunication Network consists of SELV CIRCUITS or TNV CIRCUITS. So International Standards, like as ITU-T Recommendation K.11, UL 1950, CSA C22.2 950 have been taken to reduce the risk that the Overvoltages from the power lines and from electrictraction lines, that may be received from the telecommunication network. Legal requirements may exist regarding permission to connect equipment having PTC components to a telecommunication network. Surge suppressors that bridge the insulation shall have a minimum d.c. sparkover voltage of 1.6 times the rated voltage or 1.6 times the upper voltage of the tared voltage range of the equipment. If left in place during electric strength testing of insulation, they shall not be damaged. In this work, The Conception ＆ Fail-Mode Analysis of PTC components for Over-Current Protection is proposed. It guarantees the protection for PL Claim about this Subject.

The effect of surface free energy on the positive temperature coefficient (PTC) of carbon black/thermoplastic resin composites was investigated. The thermoplastic resins such as EVA, LDPE, LLDPE and HDPE were used with the addition of 30 wt.% of the carbon black. The surface free energy of the composites was studied in the context of two-liquid contact angle measurements, i.e., deionized water and diiodomethane. It was observed that the resistivity on PTC composites Was greatly increased near the crystalline melting temperature, due to the thermal expansion of polymeric matrix. From the experimental results, it was proposed that the decrease of surface free energy induced by interactions between carbon black surfaces and polymer chains is an important factor to the fabrication of a PTC composite made of carbon black and polymeric matrix.

본 연구에서는 입계의 성질을 이용한 PTCR 재료에 입계 modifier로서 Bi2O3를 첨가하고 입계의 미세구조와 결함농도를 변화시켜 이에 따른 소결 및 전기적 특성변화를 TMA, XRD, 복합 임피던스방법 등을 이용하여 해석하였다. 실험 결과 Y이 도우핑된 BaTiO3PTCR 재료에 Bi2O3를 첨가하였을때 약 0.1mol%까지 고용이 되는 것으로 밝혀졌다. Bi2O3를 고용한계 이하로 첨가시에는 생성되는 vacancy등의 결함으로 말미암아 Y-BaTiO3의 치밀화가 촉진되었으나, 그 이상 첨가하면 치밀화 뿐만 아니라 결정립 성장도 억제되었다. Bi2O3의 첨가량에 따라 계내에 존재하는 각 이온의 반경, 결함 반응식 및 격자 탄성 변형 에너지 등을 고려하면 Y-BaTiO3결정립 내부에 Ba와 Ti vacancy가 동시에 생길 수 있어 고온저항이 높아짐을 알 수 있었다. BN은 BaTiO3에 고용이 되지 않는 것으로 밝혀졌으며 B2O3를 주성분으로한 액상형성으로 인하여 저온에서의 급격한 치밀화가 관찰되었다. 또 Ba-Y-Ti-B-O의 비정질 상이 tripie junction에 존재함으로써 상온저항이 크게 변화하였으며, PTCR jump도 높아졌다.