研究目的
To detect characteristic temperatures (Burns temperature, transition to paraelectric phase, temperature maximum of dielectric constant, intermediate temperature) in Na0.5Bi0.5TiO3-xBaTiO3 ceramics using acoustic emission and compare with previous methods to show that Burns temperature cannot be reliably determined from reverse dielectric constant deviation.
研究成果
The acoustic emission method successfully detected characteristic temperatures in NBT-xBT relaxor ferroelectrics, showing that Burns temperature cannot be reliably determined from reverse dielectric constant measurements but can be using dilatometric and AE methods. Both Burns and intermediate temperatures exhibit a minimum near the morphotropic phase boundary at x=0.06.
研究不足
The study is limited to NBT-xBT ceramics with x up to 0.8; Tp was not detected for x > 0.8. The AE method may have sensitivity constraints, and comparisons rely on previously published data which may have inconsistencies.
1：Experimental Design and Method Selection:
The study uses acoustic emission (AE) to detect characteristic temperatures in NBT-xBT ceramics, based on sharp bursts of AE signals during phase transitions.
2：Sample Selection and Data Sources:
Ceramic samples with x = 0,
3：06, 1, 2, 4, 6, and 8 were produced using conventional ceramics technique from raw powders (Na2CO3, Bi2O3, Ba2CO3, TiO2) with purity >99%. List of Experimental Equipment and Materials:
High-temperature muffle furnace with PID-controller (Eurotherm), Pt-crucible, alumina crucible, silver epoxy, fused silica acoustic rod waveguide, PZT-19 disk piezoelectric sensor, 500 kHz bandpass low-noise variable preamplifier, detector amplifier, Ch-Al thermocouple, resistance element furnace, PC for data readout.
4：Experimental Procedures and Operational Workflow:
Samples were calcined at 900°C for 3h, re-milled, pressed into discs, sintered at 1100°C for 3h, polished, and silver contacts fired. AE measurements were performed from 20–600°C at 1–3°C/min heating rate, with AE count rate recorded.
5：Data Analysis Methods:
AE count rate data were analyzed to identify temperatures TB, Tp, Tm, T* based on bursts, and dependences on x were plotted and compared with literature data.
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