New Negative Temperature Coefficient Ceramics in Ca–Ce–Nb–M–O (M=Mo or W) System

Abstract

A series of quaternary powellites with varying cerium contents in a Ca–Ce–Nb–M–O (where M=Mo or W) system has been synthesized through the solid‐state route. Powder X‐ray diffraction analysis shows that these compounds crystallize in a tetragonal powellite structure with the I41/a space group. The structure was further confirmed by Raman spectroscopic analysis. The electrical conductivity studies reveal that they exhibit negative temperature coefficient (NTC) thermistor characteristics. The characteristic parameter of the thermistor (β) is found to be in the range of 5000–7000 K, and these values can be tuned with the cerium concentration. The electrical conductivity in these compounds is due to the presence of Ce3+, which remains in the reduced state without being oxidized to Ce4+ due to the structural stabilization. The X‐ray photoelectron spectroscopy analysis corroborates the presence of Ce in the 3+ state.

Activated Carbon Obtained from Bamboo: Synthesis, Morphological, Vibrational, and Electrical Properties and Possible Temperature Sensor

“…This work reports the synthesis process and morphological, elemental, optical, and vibrational characterization of AC obtained from bamboo, determining its chemical composition, identifying vibrational response and functional groups, as well as thermal stability, which allowed proposing an approximate structure of this material and suggesting the development of NTC temperature sensors based on AC obtained from bamboo with attractive response as thermoresistive sensors . The NTC temperature sensor proposed in this work presents linear response and sensitivity at 127.7 μA K −1 in the temperature range varying from 321.1 to 447.8 K. It is low cost compared with more sophisticated non‐linear NTC thermistors …”

“…Negative temperature coefficient (NTC) temperature sensors are thermistors that, as temperature increases, decrease resistance and voltage, that is, increased concentration of charge carriers increases electrical conductivity. Furthermore, NTC thermistors have been extensively studied and manufactured according to specialized literature from SiO 2 in (Mn 1:2 Ni 0:78 Co 0:87‐x Cu 0:15 Si x ) O 4 , (Ba, Sr) TiO 3 single‐crystal films, NiMnFeCrO, ceramics in CaCeNbMO (M 5 Mo or W), MnCoNiO, Al + implanted 4H‐SiC p + −in, Pd‐loaded WO 3 , and SiCNO‐GO . Development of thermistors requires for materials exhibit high electrical conductivity and a low thermal conductivity .…”

Phase formation processes and synthesis of solid solutions in Ca-R-Nb-M-O systems

“…Deepa et al [8] studied the system Ca-Ce-Nb-M-O (where M = Mo or W). All samples Ca 2 CeNbM 2 O 12 , CaCeNbMO 8 , and CaCe 2 Nb 2 MoO 12 have cubic structure with a space group (SG) I41/a.…”

“…Electrical conductivity increases with increasing cerium concentration, which is due to the variable valence of cerium. Excess oxygen is released into the atmosphere upon heating, leaving electron in the lattice, which is further responsible for the conductivity of the compound [8].…”

Spark Plasma Sintering of Negative Temperature Coefficient Thermistor Ceramics

“…In the past few years, development of novel high temperature NTC thermistor materials has been motivated by the requirements of particle filters and catalytic converters in exhaust pipe for automotive motors [23,24]. NTC thermistor ceramics composed of spinel structure (MMn 2 O 4 , where M=Ni, Co, Fe, Cu, Zn) show aging of the electrical properties and their application is commonly limited to temperatures below 300°C [25,26]. The literature suggests that rare earth (Sm, Tb, Y, etc) perovskite oxides (ABO 3 ) can be used for measurements from ambient to 1000 • C [23].…”