Negative Thermal Expansion in Lead-Free La-Substituted Bi_0.5Na_0.5VO₃

Abstract

Negative thermal expansion (NTE) materials, which shrink upon heating, are required in modern technologies. In this study, new lead-free NTE compounds were obtained by substitution of La in PbTiO3 (PT)-type compounds, Bi0.5Na0.5VO3. Decreasing the stereochemical activity by substitution of La for Bi3+ and electron doping by substitution of La for Na+ were found to destabilize the tetragonal phase and cause a temperature-induced transition to a small cubic phase accompanied by NTE. The temperature hysteresis was suppressed because the phase transition was second order-like.

Negative thermal expansion in PbTiO₃-type perovskites oxide Bi_0.5+<i>_x</i>Na_0.5−<i>_x</i>VO₃

“…Bi 0.55 Na 0.45 VO 3 (x = 0.05) decomposes at 560 K without a noticeable change in the c/a ratio while Bi 0.5 La 0.05 Na 0.45 VO 3 with the same electron carrier concentration exhibits transition to the cubic phase accompanied by NTE with ¹2.2 % volume contraction. 23) On the The crystal structures were drawn using VESTA 3 software. 25) other hand, the splitting of the 001 and 100 peaks of Bi 0.6 Na 0.4 VO 3 (x = 0.1) gradually decreases on heating, indicating a decrease in the c/a ratio.…”

Realization of Negative Thermal Expansion in Lead-Free Bi0.5K0.5VO3 by the Suppression of Tetragonality

“…Bi 1/2 Na 1/2 VO 3 and Bi 1/2 K 1/2 VO 3 have moderate c / a ratios, which are comparable to that of PT, indicating their applicability as lead-free NTE materials . NTE can be successfully achieved in modified Bi 1/2 Na 1/2 VO 3 by substituting both Bi 3+ (suppression of the 6s 2 lone pair effect) and Na + (electron-donating to V 4+ ) with La 3+ . As electron doping has been found to effectively suppress the c / a ratio and induce NTE in PbVO 3 and Bi 1/2 Na 1/2 VO 3 , ,, in the present experiment, electron doping in Bi 1/2 K 1/2 VO 3 was conducted by substituting K + with La 3+ .…”

“…A series of Bi 0.5 K 0.5– x La x VO 3 ( x = 0.0–0.10) compounds were synthesized in a cubic anvil-type high-pressure apparatus under high-pressure and high-temperature conditions. The raw materials of Bi 2 O 3 , KVO 3 , La 2 O 3 , and V 2 O 3 were mixed well at stoichiometric ratios and then treated at 8 GPa and 1473 K for 1 h. ,, Powder X-ray diffraction (XRD) patterns were collected on a Bruker D8 ADVANCE diffractometer for phase identification. Synchrotron X-ray powder diffraction (SXRD) data for structural refinements were collected at the BL02B2 beamline of SPring-8 at λ = 0.42018 Å and analyzed by the Rietveld method in the RIETAN-FP program. , …”

“…NTE can be successfully achieved in modified Bi 1/2 Na 1/2 VO 3 by substituting both Bi 3+ (suppression of the 6s 2 lone pair effect) and Na + (electron-donating to V 4+ ) with La 3+ . As electron doping has been found to effectively suppress the c / a ratio and induce NTE in PbVO 3 and Bi 1/2 Na 1/2 VO 3 , ,, in the present experiment, electron doping in Bi 1/2 K 1/2 VO 3 was conducted by substituting K + with La 3+ . Both composition- and temperature-induced tetragonal-to-cubic phase transitions were achieved in Bi 0.5 K 0.5– x La x VO 3 compounds.…”

Energy transfer-triggered multicolor emissions in Tb3+/Eu3+-coactivated Y2Mo3O12 negative thermal expansion microparticles for dual-channel tunable luminescent thermometers

“…Please do not adjust margins Please do not adjust margins unit cell is decreased with rising the temperature, is increasing since they are able to be used to adjust the thermal expansion coefficient of other compounds. 18,19 and put them into a beaker, in which 200 mL of deionized water was filled. Afterwards, the citric acid (10 mmol) was weighted and put into the above solution and strongly stirred to allow them to be dissolved.…”