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What is the lowest temperature tungsten starts sublimating at? I've tried to search in Google but without any luck.

For example, $\ce{WO3}$ starts sublimating roughly at $\pu{550 °C}$, according to the paper Growth of epitaxial tungsten oxide nanorods.

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    $\begingroup$ There is no such thing. Any compound has some vapor pressure at any temperature. Of course, for tungsten at room temperature it would be negligibly low. If you want to know when the pressure hits some particular threshold, define the threshold first. $\endgroup$ – Ivan Neretin May 5 '16 at 5:50
  • $\begingroup$ Let's say 0.001 Pa. $\endgroup$ – Capo Pavel Mestre May 5 '16 at 7:14
  • $\begingroup$ Now that's a sensible question. Wait a sec, I'll check my figures. $\endgroup$ – Ivan Neretin May 5 '16 at 8:01
  • $\begingroup$ Maybe it would be better to share your figures, since I might want to know the temperature at a different pressure... :) $\endgroup$ – Capo Pavel Mestre May 5 '16 at 8:09
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Well, you see, searching online for "vapor pressure at such-and-such temperature" (or conversely, "temperature to get such-and-such pressure") is often fruitless, and unnecessary too, because pretty decent approximations are known. Here is one: $$\ln\mathfrak p=-{\Delta H\over R}\left({1\over T}-{1\over T_0}\right)$$ where $\mathfrak p$ is your vapor pressure in atmospheres, $\Delta H$ is the enthalpy of vaporization and $T_0$ is the boiling temperature at normal pressure. For tungsten, the latter two are reported as 774 kJ/mol and 6203 K, respectively. Now you may plug in your desired pressure and solve for temperature.

That's a relatively crude approximation, for the enthalpy will hardly remain constant over such a wide range of temperatures. This page may contain better approximations designed for specific ranges.

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    $\begingroup$ Kurt J. Lesker has a gigantic table of materials and the temperatures at which they achieve a vapour pressure of $10^{-8}$, $10^{-6}$ and $10^{-4}\ \mathrm{torr}$. For tungsten, these are $2117$, $2407$ and $2757\ \mathrm{ºC}$, respectively. For $\ce{WO3}$, only the highest vapour pressure has a tabulated temperature, at $980\ \mathrm{ºC}$ $\endgroup$ – Nicolau Saker Neto May 5 '16 at 10:06
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    $\begingroup$ This answer only works for liquids, not solids. For sublimation, you need the enthalpy of sublimation and a reference vapor pressure for the solid at some temperature (as you stated, this would be crude as the enthalpy of sublimation would change with T). $\endgroup$ – S. Burt May 5 '16 at 22:18
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    $\begingroup$ @S.Burt True, I forgot to mention that. Well, one may calculate the vapor pressure at melting point to use that as a reference, and simply add together the enthalpies of melting and vaporization... but that would mean building one crude approximation on top of the other. All in all, that's one more reason for resorting to some empirical formula. $\endgroup$ – Ivan Neretin May 6 '16 at 6:15
  • $\begingroup$ I've never seen pressure denoted with a Fraktur character $\mathfrak p$ in non-German texts. Does it mean anything specific? $\endgroup$ – andselisk Jan 30 at 8:48
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    $\begingroup$ @andselisk No. Quite a few years ago, my physical chemistry professor used to write it like that, probably for no other reason than his professor did the same before him, and so on. $\endgroup$ – Ivan Neretin Jan 30 at 8:53

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